Yokai Bestiary 5E: Integrating Japanese Folklore into Tabletop Roleplaying Mechanics

Audio review: "Yokai Bestiary 5E"

The translation of Eastern folklore into the mechanical frameworks of  tabletop roleplaying games presents a unique design challenge. Traditional fantasy roleplaying, particularly within the Fifth Edition (5E) ruleset, is heavily predicated on asymmetrical combat paradigms where the ultimate resolution is often the physical destruction of the adversary. Conversely, Japanese mythology and the vast pantheon of yokai (spirits, demons, and supernatural phenomena) operate on an entirely different philosophical axis. Yokai are frequently manifestations of neglected emotions, discarded objects, environmental warnings, or karmic retribution. Defeating or surviving them often requires appeasement, trickery, psychological fortitude, or the observation of specific cultural rituals rather than mere martial superiority.   

The Yokai Bestiary 5E, authored by Sergiusz Junczyc and published by A4 Play, represents a highly structured and ambitious attempt to bridge this cultural and mechanical divide. Featuring over forty distinct entities drawn directly from Japanese legend, the supplement is specifically engineered for adventuring parties operating in the second tier of play (levels 7-10), with a particular focus on smaller groups of one to three players. The following review provides an exhaustive, granular evaluation of the publication, analyzing its structural design, the fidelity of its folkloric adaptations, its mechanical innovations.   

Structural Design and Pedagogical Layout

A critical component of any tabletop roleplaying supplement is its usability at the table. Game Masters (GMs) require information to be presented in a manner that minimizes cognitive load during active gameplay. The Yokai Bestiary 5E addresses this through a rigid, user-friendly "two-page spread" format.   

For the vast majority of the creatures detailed in the text, the left-hand page is entirely dedicated to narrative context and folklore. This includes a retelling of the original myths, an analysis of the creature's behavior, and specific recommendations that guide the referee on how to roleplay the entity or telegraph its weaknesses to the players. The right-hand page is strictly mechanical, containing the 5E stat block, combat traits, actions, and distinct adventure hooks. This strict separation of lore and mathematics ensures that a Game Master does not need to flip pages during a combat encounter, a design choice that has been universally praised in consumer evaluations.  

The Ecology of the Tsukumogami

One of the most mechanically fascinating aspects of Japanese folklore adapted in this volume is the concept of the Tsukumogami—mundane household objects that acquire a spirit and sentience after one hundred years of existence. The supplement dedicates a significant portion of its design to these entities, presenting them not as lethal, world-ending threats, but as mischievous, often resentful tricksters that punish humans for neglecting their possessions.   

Creature Name	Base Object	Challenge Rating	Key Mechanical Trait	Primary Combat Action
Biwa Bokuboku	Lute	CR 1	Musical Sentience, Non-Aggressive Nature	Soothing Melody, Ballad of Twilight
Boroboroton	Tattered Futon	CR 2	Naptime Stalker, Blanket Disguise	Flap Slap, Smother (Grapple)
Bura-Bura	Paper Lantern	CR 2	Eerie Glow, Paper Body (Fire Vulnerability)	Spook, Flare of Light
Kosode-No-Te	Kimono	CR 2	Apparition of Arms, Eerie Hover	Sleeve Claw, Ghostly Embrace
Seto Taisho	Ceramic Dishware	CR 2	Ceramic Construction, Reassemble	Chopstick Strike, Smash & Scatter
Karakasa	Paper Umbrella	CR 3	Hopping Movement, Umbrella Disguise	Tongue Slap, Umbrella Shriek
Mokumokuren	Shoji (Paper Screen)	CR 4	Bound to the Frame, Eyes Everywhere	Ghostly Eye, Terror Gaze

The mechanical synthesis of these creatures is exceptional. Rather than assigning them high damage outputs, the design focuses on status effects, illusions, and psychological manipulation. For example, all Tsukumogami share a resistance to nonmagical bludgeoning, piercing, and slashing damage, reflecting the supernatural durability of their newly animated forms.   

The Mokumokuren (CR 4), a spirit composed of dozens of blinking eyes residing in torn paper screens, possesses a movement speed of zero feet, as it is strictly "Bound to the Frame". It can only move by sliding across connected partitions within a building. Its primary offensive capability is a "Terror Gaze" that frightens intruders, and a "Ghostly Eye" ranged spell attack dealing psychic damage. This forces players into a spatial puzzle: rather than fighting a mobile enemy in an open field, they must navigate a haunted environment where the architecture itself observes and attacks them.   

Similarly, the Boroboroton (CR 2) operates as an ambush predator of the bedroom. With its "Naptime Stalker" trait, it gains advantage on Stealth checks against sleeping creatures and can move seamlessly into their spaces. Its combat loop relies on the "Smother" action, which restrains and blinds a target while suffocating them. This perfectly encapsulates the domestic horror of the original folklore, where a discarded, unappreciated blanket seeks vengeance on its neglectful owner.   

The Seto Taisho (CR 2) introduces a unique physical mechanic. Composed of discarded teacups and sake bottles, it possesses a "Ceramic Construction" trait that causes it to take automatic bludgeoning damage if knocked prone or dropped. However, its "Reassemble" ability allows it to reform from its shattered pieces over one minute if the fragments are not scattered by the players. This transforms a simple combat encounter into a cleanup operation, requiring players to actively bag or disperse the shards to secure a permanent victory.   

The text also highlights the Biwa Bokuboku (CR 1), an animated lute that represents the completely non-combative extreme of the Yokai spectrum. It possesses a "Non-Aggressive Nature" trait, refusing to attack entirely. Instead, it utilizes a "Soothing Melody" to charm aggressors and a "Ballad of Twilight" to lull them into a half-dream state, halving their speed and impairing their initiative. This requires the GM to design encounters focused on diplomacy, curiosity, or musical interaction rather than tactical combat, greatly enriching the roleplaying experience.   

Vengeance, Tragedy, and the Onryo

The bestiary adapts of Onryo and Yurei—vengeful spirits bound to the physical realm by intense negative emotions, betrayal, or trauma. These entities are characterized by potent curses, psychological warfare, and specific narrative triggers that must be navigated carefully.

Hashihime (The Bridge Princess)

The Hashihime (CR 7) originates from the tragic tale of Kunitoki, a woman who drowned herself in the Uji River following her husband's infidelity, transforming into a demon fueled by sheer jealousy. Mechanically, she is a Medium fiend with a formidable Armor Class of 16 and 110 hit points. Her folklore is vividly represented through her "Torch Bite" action, which deals piercing and fire damage, mimicking the legend where she clamped a burning double-ended torch between her teeth during her transformation.   

Most notably, her "Fury of Jealousy" bonus action allows her to focus her rage on a creature she perceives as "happy" or "content," granting her advantage on attacks against them while imposing disadvantage on their saving throws against her spells. This psychological targeting forces players to consider their characters' emotional states and interpersonal dynamics during combat, an innovative narrative vector rarely seen in standard 5E design.   

Futakuchi-Onna (The Two-Mouthed Woman)

The Futakuchi-Onna (CR 6) embodies the consequences of avarice and hidden sins. Appearing as a standard human woman, she conceals a ravenous, independent second mouth beneath her hair. The mechanical representation of this duality is profound: the "Dual Mouth" trait explicitly states she cannot be rendered mute by any magical effect, as the secret mouth operates independently. In combat, she utilizes "Living Hair" to grapple foes with a 10-foot reach, pulling them into the "Gnashing Bite" of her hidden maw, which deals an additional 7 (2d6) necrotic damage to grappled targets as it devours both flesh and spirit. Furthermore, the second mouth acts as an involuntary confessor, babbling the woman's past crimes against her will, providing Game Masters with an excellent method for dispensing lore or solving investigative mysteries mid-combat.   

Yuki-Onna (The Snow Woman)

The Yuki-Onna (CR 6) is the manifestation of the lethal, indifferent cold of mountain blizzards. Operating as an ethereal undead, she possesses a "Snowbound Form" that renders her lightly obscured during snowfall and grants her advantage on Stealth checks in wintry environments. Her combat loop is designed around systematic immobilization: her "Winter's Gaze" requires a DC 15 Constitution save to avoid paralysis, while her "Frost Touch" significantly reduces the target's speed. The lore provided heavily emphasizes that she occasionally spares victims who exhibit remarkable courage or who intrigue her, giving players a mechanical and narrative incentive to stand their ground and negotiate rather than flee, as outrunning the storm is mathematically impossible.   

Kuchisake-Onna (The Slit-Mouthed Woman)

The modern urban legend of the Kuchisake-Onna (CR 6) is translated into a terrifying ambush predator. Armed with scissors and a surgical mask, her core mechanic revolves around her "Am I Pretty? (Frightful Ensnarement)" ability. She forces a target to make a Wisdom saving throw; on a failure, the victim is paralyzed by dread and compelled to respond politely. The combat encounter becomes a high-stakes dialogue puzzle, where evasive answers or specific cultural countermeasures (such as chanting "pomade" or "lipstick") are required to break her psychological hold before she utilizes her "Face Slash" bonus action, which inflicts lasting Charisma penalties on the victim. 

Dorotabo (The Mud Farmer)

The Dorotabo (CR 4) is the spirit of an elderly farmer whose hard-won rice paddies were neglected or squandered by ungrateful heirs. Rising from the mud as a one-eyed, three-fingered monstrosity, its existence is driven entirely by agricultural rage. While its Challenge Rating is relatively low, its thematic integration is strong; it operates as an environmental hazard within swampy fields, utilizing the terrain to exact revenge on those who disrespect the labor of their forebears.   

The Tricksters: Illusions, Bargains, and Nature Spirits

Not all Yokai seek the destruction of mortals; many are merely territorial, mischievous, or possess an alien morality. The text provides highly nuanced mechanics for the primary shapeshifting tricksters of Japanese myth, requiring players to utilize insight and investigation rather than brute force.

The Kitsune

The Kitsune (CR 5) is a highly intelligent shapeshifting fox spirit capable of alternating between a mundane fox, a humanoid guise, and a hybrid form. Their danger lies not in brute strength, but in extreme evasion and enchantment. With an AC of 15, high Dexterity and Charisma, and a suite of innate spells including mislead, mirror image, and charm person, a Kitsune can easily dismantle a party's cohesion without dealing physical damage.   

The "Beguiling Kiss" ability forces a Charisma saving throw; on a failure, the target is charmed and slowly drained of vitality, taking 5 (1d10) psychic damage each turn as the Kitsune siphons their life force. Furthermore, the "Flickering Reflection" trait establishes a hard mechanical rule for revealing their true nature: their illusions falter when viewed in a mirror or still water, requiring a DC 15 Perception check to pierce the veil. This embeds a classic folklore trope directly into the investigative mechanics of the game.   

The Tanuki

In contrast to the elegant and sometimes malicious Kitsune, the Tanuki (CR 5) is presented as a jovial, chaotic neutral fey. Known for their love of sake and pranks, their mechanics are heavily weighted toward confusion and non-lethal disruption. Their signature ability, "Leaf Illusions," allows them to transform ordinary leaves into illusory coins or trinkets that revert upon close inspection (DC 15 Investigation). In combat, they utilize a "Trickster's Taunt" to inflict the confusion spell effect via a psychic barrage of mockery. Their defensive reaction, "Dodge and Weave," allows them to impose disadvantage on an incoming attack by dissolving into a swirl of leaves and teleporting 10 feet. The GM notes emphasize that Tanuki rarely fight to the death and can easily be bribed with sweet potatoes or alcohol, promoting alternative, non-violent encounter resolutions.   

The Kappa

The Kappa (CR 6) is a masterful blend of amphibious biology and rigid cultural etiquette. Dwelling in rivers and lakes, this monstrosity possesses an "Aquatic Ambusher" trait granting stealth superiority in water. Its combat strategy relies on grappling opponents and using the "Drag Below" bonus action to pull victims underwater to drown them or extract their souls via the "Steal Intellect" ability.   

However, the genius of the Kappa's design lies in the "Dish of Power (Sara)" trait. A hollow atop the Kappa's head is filled with water, granting it advantage on Strength checks, rapid health regeneration (5 HP per turn), and enhanced damage. If a player knows the folklore, they can attempt to force the Kappa to bow—either through a contested Strength check or by exploiting its cultural compulsion to return a polite greeting. If forced to bow or knocked prone, the water spills, and the Kappa immediately loses all its buffed attributes until it can submerge its head again. This translates a highly specific cultural myth into a dynamic, highly interactive combat mechanic.   

Jinmenju (The Human-Faced Tree)

The Jinmenju (CR 2) operates as an interactive environmental set piece rather than a monster. A massive tree bearing fruit that resembles laughing or crying human heads, it is rooted in place with a speed of zero. Its threat is minimal, mostly relying on "Falling Fruit" to bludgeon those beneath its canopy. However, its true value lies in its "Memory Fruit" mechanic. If a player consumes the fruit, they gain dreamlike glimpses of the dead's memories, granting advantage on History checks, but risking a Wisdom saving throw failure that renders them memory-addled and confused for hours. This transforms the Yokai into a high-risk, high-reward information repository for questing adventurers.   

The Grotesque, the Surreal, and the Uncanny

A defining characteristic of Japanese folklore is the prevalence of the bizarre and the surreal—entities that defy Western categorization of monsters. The Yokai Bestiary 5E captures this uncanny valley perfectly through mechanics that emphasize revulsion, absurdity, and psychological distress.

Creature Name	Type/Subtype	Challenge Rating	Signature Surreal Mechanic
Ashiarai Yashiki	Fey (Giant Foot)	CR 6	Demanding Bath, Rafter-Wrecker
Nuppeppo	Ooze (Flesh Blob)	CR 4	Stench of Decay, Strange Flesh
Akaname	Fey (Filth Licker)	CR 2	Filth Feeder, Sticky Residue
Noppera-Bo	Fey (Faceless Ghost)	CR 5	Faceless Revelation, Illusory Mask
Te-No-Me	Undead (Hand Eyes)	CR 5	Palmsight, Palm Gaze
Konaki-Jiji	Fey (Heavy Infant)	CR 5	Misleading Cry, Weighted Embrace
Obariyon	Fey (Heavy Spirit)	CR 5	Leap & Latch, Strange Reward
Tofu-Kozo	Fey (Tofu Boy)	CR 4	Tempting Tofu (Fungal Disease)

 

Ashiarai Yashiki (The Foot-Washing Mansion)

Perhaps the most surreal entry in the entire text is the Ashiarai Yashiki (CR 6). This entity manifests solely as a gargantuan, muddy, and bloody foot that crashes through the ceiling of a building at night, bellowing a demand to be washed. Mechanically, the creature has a speed of 0 ft. due to its "Partial Manifestation" trait; it is anchored to its entry point and cannot be forcibly displaced. It deals double damage to objects and structures. If the inhabitants refuse to wash it, it unleashes a "Foot Quake," a massive area-of-effect stomp that collapses the structure around the players.   

However, the encounter is instantly won if a player uses an action, water, and soap, and succeeds on a DC 14 Charisma (Persuasion) check to thoroughly cleanse the appendage, causing it to vanish peacefully. This is a masterful execution of surreal folklore, rewarding players for engaging with the bizarre narrative and performing domestic chores rather than drawing their swords.   

Nuppeppo

The Nuppeppo (CR 4) is a sagging, ambulatory mass of rotting flesh. It possesses a "Non-Aggressive Nature" and will slowly ooze away if encountered. However, its defense lies in its "Stench of Decay," forcing Constitution saves to avoid poisoning, and its "Amorphous Bulk," which leaves behind a greasy residue that creates difficult terrain. The true mechanical hook of the Nuppeppo, however, lies in its optional "Strange Flesh" rule: legend dictates that consuming its vile meat grants superhuman strength or eternal life. The GM is encouraged to offer players a profound boon (such as immunity to aging or disease) paired with a terrible curse or physical transformation if they manage to kill and eat the sickening creature.   

Akaname (The Filth Licker)

The Akaname (CR 2) is a small, goblin-like entity with a prehensile tongue that infiltrates poorly maintained bathhouses at night to consume grime. While physically weak, its "Filth Feeder" trait allows it to regenerate hit points in dirty environments, and its "Sticky Residue" leaves behind a supernatural slime that reduces the movement speed of anyone who steps in it. Furthermore, its "Tongue Lash" attack carries a disease that imposes disadvantage on saving throws against natural illnesses. It represents the gamification of hygiene, punishing players who neglect their living quarters.   

Te-No-Me (The Hand Eyes)

The Te-No-Me (CR 5) is the vengeful spirit of a blind merchant murdered by bandits, reborn with bulging, bloodshot eyes embedded in the palms of its hands. Its "Palmsight" mechanic is exceptionally creative: when its hands are closed, it is effectively blinded beyond 10 feet. When it opens its hands to reveal its eyes, it gains blindsight out to 30 feet, allowing it to accurately hunt in the dark graveyards it haunts. It utilizes a "Palm Gaze" to paralyze victims with supernatural dread, reflecting its unending search for the faces of its killers.   

Obariyon and Konaki-Jiji

Both the Obariyon (CR 5) and the Konaki-Jiji (CR 5) weaponize the mechanic of encumbrance and human empathy. The Obariyon masquerades as a child in the woods, leaping onto a traveler's back. Once attached via the "Leap & Latch" ability, it becomes magically heavier each round, reducing the target's speed cumulatively until they are crushed prone. However, if a player manages to endure the weight and carry the Obariyon for 100 feet without collapsing, the "Strange Reward" mechanic activates, and the Yokai departs peacefully, leaving behind a pouch of gold coins.   

The Konaki-Jiji operates similarly but with malicious intent. It utilizes a "Misleading Cry" (requiring an Insight check to discern from a real baby) to lure victims. Once picked up, its "Weighted Embrace" engages, dealing continuous bludgeoning damage as it turns to stone. Unlike the Obariyon, the Konaki-Jiji offers no reward; it bites the restrained victim and emits a "Maddening Giggle" that forces a fear save across the battlefield, serving as a lethal trap for overly compassionate adventurers.   

Maritime Terrors: The Ocean's Wrath

Japanese folklore, shaped heavily by the archipelago's historical reliance on the sea, is rich with oceanic horrors. The Yokai Bestiary 5E provides highly detailed mechanics for maritime campaigns, ensuring that ocean travel is fraught with psychological and physical peril.

Umi-Bozu (The Sea Monk)

The Umi-Bozu (CR 8) is a colossal, formless black silhouette that rises from the ocean at night to shatter ships. As a Huge undead entity with 189 HP and a Strength score of 22, it is a physical powerhouse. Its primary threat is the "Capsize" action, allowing it to easily flip Large or smaller vessels, and engage in contested Athletics checks to upend even Huge ships, throwing entire adventuring parties into the freezing water. Once in the water, it utilizes its "Watery Embrace" to grapple and restrain victims, dealing continuous cold damage.   

The folklore advises sailors to pretend to sleep and ignore the beast; speaking to it invites immediate destruction. The text translates this into an adventure dynamic where the sheer scale of the creature encourages evasion, silence, and stealth over direct confrontation, turning a naval journey into a tense survival sequence.   

Funa-Yurei (The Ghost Ship)

The Funa-Yurei (CR 7) represents the restless souls of drowned mariners. These spirits approach living vessels and demand a bailer (a scoop) to fill the players' boat with water and sink it. Mechanically, the Funa-Yurei is a Medium undead with a fly and swim speed. It utilizes "Tidal Lure" to project illusory lights, tricking navigators into crashing upon reefs (requiring DC 14 Insight checks to discern the deception).   

In combat, its "Drowning Touch" forces a Constitution save; on a failure, the target runs out of breath, unable to speak or cast spells with verbal components. Furthermore, its "Phantasmal Undertow" creates a 20-foot cube that drags characters deep underwater, restraining them with ghostly hands. The GM notes emphasize the classic folkloric countermeasure: handing the spirits a bottomless scoop (a ladle with holes drilled in it) mathematically nullifies their ability to sink the ship, rewarding player preparation and mythological research.   

Bake-Kujira (The Ghost Whale)

The Bake-Kujira (CR 8) is the skeletal apparition of a slaughtered whale, accompanied by a swarm of macabre, unidentified birds. It operates with an "Ethereal Undercurrent" trait, allowing it to phase through solid aquatic barriers. Its "Phantasmal Presence" dictates that nonmagical harpoons and spears pass harmlessly through its skeletal frame, drastically reducing the efficacy of standard naval weaponry. The swirling "Spectral Birds" that surround it impose disadvantage on all ranged weapon attacks, forcing players into perilous close-quarters combat on the open water. Encountering a Bake-Kujira is tied to the spread of curses, plagues, and fires, making it a harbinger of campaign-level disasters if left unappeased.   

Amemasu

The Amemasu (CR 7) is a colossal fish spirit capable of triggering earthquakes and floods, which occasionally assumes the form of a beautiful woman to lure young men to their deaths. Its "Shapechanger" ability allows it to alternate between humanoid and aquatic forms. In its humanoid guise, its "Freezing Touch" inflicts cold damage and numbs the victim's limbs, imposing disadvantage on attacks. When reverting to its true form, it utilizes a "Maelstrom Rush" to pull targets underwater, followed by a devastating "Swallow Whole" mechanic that traps players in its acidic maw, forcing them to deal internal damage to secure their release.   

Predators of the Deep Forests and Mountains

The untamed wilderness of Japan serves as the backdrop for some of the most cunning and lethal Yokai in the text, creatures that rely on mimicry and illusion to isolate their prey.

Tsuchigumo (The Earth Spider)

The Tsuchigumo (CR 6) is a massive, highly intelligent arachnid yokai that specializes in deception and traps. The lore recounts legendary samurai, such as Minamoto no Yorimitsu, battling these beasts. The text emphasizes that Tsuchigumo utilize multi-layered illusions to secure their meals. They frequently disguise themselves as injured travelers, elderly monks, or helpful hermits offering tea in warm, inviting cabins. Once a party's guard is down, they strike, binding victims in iron-strength webs. The GM notes heavily stress that piercing the first illusion is rarely enough; the Tsuchigumo always prepares a secondary trap, forcing players to remain paranoid even after seemingly uncovering a ruse.   

Nure-Onna (The Wet Woman)

The Nure-Onna (CR 7) haunts shorelines and riverbanks, appearing as a weeping woman with the lower body of a massive serpent. She weaponizes maternal instinct by begging travelers to hold her swaddled "child" so she can rest. The moment the bundle is accepted, it magically increases in weight—similar to the Konaki-Jiji—pinning the victim to the ground. With the target immobilized, the Nure-Onna strikes, utilizing her serpentine strength to drain their blood. This creates a high-stakes social encounter prior to rolling initiative, where insight and suspicion are the only defenses against immediate physical incapacitation.   

Yamamba and Onibaba (The Mountain Hags)

The Yamamba (CR 6) and Onibaba (CR 7) represent the archetypal mountain witches, though they operate with distinct methodologies. The Yamamba embodies the duality of the wild—she can be a nurturing mother figure to heroes (like the legendary Kintaro) or a cannibalistic predator. Mechanically, she is a chaotic evil monstrosity with innate spellcasting (disguise self, hold person, polymorph). Her "Illusory Guise" allows her to appear as a harmless old woman offering shelter. In combat, her "Serpentine Locks" reflexively strike nearby enemies with poison damage, while her "Devouring Maw" forces a Strength save to avoid being pulled into her distended jaws for massive piercing damage.   

The Onibaba, conversely, is rooted in pure human tragedy and madness. Originating from the tale of a mother who unknowingly murdered her own pregnant daughter to harvest a liver, she is now a demonic cannibal. She utilizes "Mountain Cunning" to effortlessly navigate rocky terrain and ambush travelers. Her signature weapon, the "Bone Knife," inflicts necrotic damage and poisons the target, representing the lingering malice of her victims.   

Colossal Threats and Scalable Adversaries

To accommodate high-level campaigns and provide epic, world-altering threats, the Yokai Bestiary 5E features scalable stat blocks for its most iconic monsters, providing standard, "Titan/Elite," and "Apocalypse/Overlord" variants. This structural choice is highly effective, allowing GMs to utilize the same thematic lore across multiple tiers of play.   

Tesso: The Iron Rat

The Tesso is born from the obsessive rage of Raigo Ajari, a Buddhist monk who starved himself to death in protest against a broken promise by the Emperor, returning as an iron-skinned rat-demon.   

Base Tesso (CR 7): A Large fiend with AC 17 and 127 HP, possessing "Iron Hide" (resistance to all nonmagical physical damage). It can summon rat swarms and possesses a unique "Devour Manuscript" ability, instantly consuming and erasing written knowledge forever—a terrifying prospect for wizards or scholars relying on spellbooks.   

Tesso, The Rat Overlord (CR 15): The AC scales to 19, HP to 257. Its rat mastery expands to command any rat within 100 feet automatically. It gains "Gnawing Hex," stunning enemies with psychic phantom rats, and Legendary Resistances.   

Tesso, Devourer of Temples (CR 20): A Huge fiend with AC 22 and 430 HP. Its "Iron Hide (Epic)" requires adamantine or magical weapons to bypass. It commands "Rat Legions" and acts as an apocalyptic plague, easily capable of leveling entire cities through sheer attrition and swarming mechanics.   

Wanyudo: The Wheel Monk

The Wanyudo is the soul of a cruel feudal lord bound to a flaming cartwheel, condemned to patrol roads and drag sinners to hell.   

Base Wanyudo (CR 8): A Large undead hovering above the ground with an AC of 17. Its "Nightmare Presence" forces anyone looking at it to make a DC 16 Wisdom save or become frightened, taking 7 (2d6) psychic damage each turn. It utilizes a "Flaming Overrun" to trample multiple targets simultaneously.   

Wanyudo, Hellfire Wheel (CR 15): Gains a "Hellish Flame Body" that burns anyone ending their turn in its space. Its overrun damage increases significantly, and it acquires a "Severing Curse" that reduces movement speed and inflicts psychic pain whenever the target attempts to attack.   

Wanyudo, Overlord (CR 20): A Huge entity with AC 20 and 472 HP. Its "Hellish Overrun" deals a staggering 49 (14d6) fire damage. Furthermore, it generates Lair Effects such as "Flaming Skies," raining embers across the battlefield, and "Shrieking Souls," imposing disadvantage on saves against its fear effects.   

Gashadokuro: The Starving Titan

The Gashadokuro is a colossal skeleton assembled from the unburied bones of those who died of starvation or in battle.   

Base Gashadokuro (CR 13): A Huge undead with AC 18 and 230 HP. Its defining mechanic is "Mass Grave Essence": if it reduces a living creature to 0 HP, it instantly absorbs their bones, regaining 20 HP and rendering the victim impossible to resurrect without 9th-level magic (true resurrection). It also possesses "Skeletal Disassembly," allowing it to detach a portion of its body to act independently as a Bone Naga, sacrificing its own HP to create tactical flanking advantages in tight spaces.   

Titan (CR 15) and Apocalypse (CR 20): While the specific numerical adjustments for these higher-tier variants occupy pages 94-95, the overarching design philosophy dictates exponential scaling of the Mass Grave Essence and area-of-effect crushing attacks. To defeat it, the GM notes emphasize the necessity of destroying the skull to collapse the entire structure, turning a massive war of attrition into a targeted tactical strike.   

Oni and Tearai-Oni

The traditional Oni (CR 7) is a staple of Japanese myth—a hulking, horned ogre-like fiend wielding a massive kanabo (iron club). The lore includes references to famous Oni like Shuten Doji and Ibaraki, noting that despite their immense power, they are often outwitted by human cunning.   

The book provides a mind-bogglingly colossal variant, the Tearai-Oni (CR 13), a Gargantuan entity whose sole purpose is washing its massive hands in mountain rivers. With a Strength score of 30 and a "Colossal Figure" trait, the Tearai-Oni's mere footsteps trigger localized earthquakes, requiring DC 18 Dexterity saves to avoid falling prone. It possesses an "Indifferent Nature," ignoring the party unless severely provoked, treating humanoids as mere insects. If engaged, its "Massive Sweep" deals 42 (12d6) bludgeoning damage across a 20-foot cone. Furthermore, its "River Ablutions" create severe environmental hazards; submerging its hands can trigger flash floods that pull characters downstream, making the creature function as a natural disaster rather than a standard combatant.   

Anomalous Entities and Environmental Obstacles

Several Yokai in the bestiary defy combat logic entirely, acting as environmental obstacles or puzzle encounters rather than traditional foes.

The Nurikabe (CR -) manifests as a massive, invisible plastered wall that suddenly blocks a traveler's path at night. As denoted by its lack of a Challenge Rating, it is not designed to be fought and killed. Attempts to walk around it fail, as the wall simply extends infinitely to the sides. The lore provides the mechanical solution: striking the lower portion of the wall with a stick weakens its magic, causing it to retreat or vanish, allowing passage.   

Similarly, the Nobiagari (CR -) is listed without a combat rating, acting as a supernatural phenomenon that grows larger the higher one looks at it. The Tengu (CR 8), highly intelligent avian humanoids that act as martial arts masters and guardians of the mountains, operate with strict hierarchies, scaling up to the Elite Commander (CR 15) and Grandmaster (CR 20). Legends note that Tengu can be petitioned for martial training, allowing GMs to use them as severe, high-level mentors rather than standard antagonists.   

Other specialized Yokai include the Azuki-arai (CR 3), a mysterious spirit heard washing beans near rivers; the Rokurokubi (CR 5), humans cursed with necks that stretch to impossible lengths at night; and the Zashiki-warashi (CR 1/8), a child spirit that brings immense fortune to a household if treated well, but economic ruin if driven away.   

Market Positioning

In the current 5E ecosystem, Asian-inspired bestiaries are gaining immense traction. Rather than a dense, 350+ page setting guide demanding heavy integration and reading time, Sergiusz's bestiary is modular, concise, and highly accessible. The rigid two-page spread format allows a GM to extract a single creature, read its lore in two minutes, and drop it seamlessly into any existing campaign, a feature highly lauded in community feedback.   

This modularity is further evidenced by A4 Play's rapidly expanding catalog. Sergiusz Junczyc has utilized the exact same design philosophy and layout structure across a series of successful projects, including the Witchwood Bestiary 5E (Eastern European folklore), the Korean Bestiary 5E, and Yokai Bestiary 5E - Book Two. By standardizing the pedagogical layout, Sergiusz has created a highly reliable pipeline for GMs seeking exotic, well-researched mythological encounters that require minimal preparation time. 

Conclusion

Sergiusz Junczyc and the team at A4 Play have successfully bypassed the common pitfall of simply reskinning standard fantasy monsters with Japanese names. Instead, they have drilled down into the behavioral idiosyncrasies and philosophical underpinnings of the folklore itself.   

By engineering stat blocks that reward players for engaging with the mythology—whether through appeasement, cultural knowledge, or exploiting specific narrative weaknesses—the bestiary elevates the standard 5E combat loop into an exercise in folkloric investigation. Coupled with its highly accessible two-page layout, scalable boss encounters, the Yokai Bestiary 5E stands as an indispensable tool for Game Masters seeking to infuse their campaigns with the surreal and terrifying elements of Japanese folklore.

Link to the book