#Hidden Hannya

Contents

Canon. Of the 3 human conspiratorial factions, the one devoted to forbidden experiments and reverse sealing.

#Opening Scene — Anatomy of Coexistence

The back room of the old clinic smelled more of medicine than of scent. The patient was a daimyo's young heir; his wrist was wrapped in a sealing talisman. The characters on the talisman were not written to block the outside — they were written to bore inward.

"This child was not devoured by a yoma," the physician Akiyama Izen said. "He is learning to live alongside one."

When the PCs opened the ledger beside the bed, they recognized the seal — the old archive stamp of the Enryokan. Below it, someone had added new writing. Coexistence has failed. Control is required.

The child opened his eyes. One eye was human; the other was red, like an oni not yet born.

"Sensei." The child whispered. "I'm hungry."

Izen smiled gently. "Bear with it a little longer. Tonight, good material has arrived."

He looked at the PCs. A doctor's eyes — not a killer's eyes, but the eyes of a person who had already calculated where to cut.

"The Enryokan tried to understand. That is why they failed. We will understand, and then we will rebuild."

#Law — Using Hidden Hannya

Hidden Hannya are human researchers, not yoma worshippers. That is what makes them more dangerous.
An incident must include a test subject, a sponsor, research records, and a failed treatment case.
Even after Hidden Hannya is defeated, the problem of what to do with the test subjects and victims remains.

#Faction Card

Item	Detail
Surface	Clinics, apothecaries, seal research facilities, artisan workshops, domain secret treatment rooms
Hidden	Oni transformation, possession, fiend transformation, reverse sealing, karakuri fusion experiments
Leadership	Reverse-sealing physicians, defrocked monks, Enryokan heirs, artisan sponsors
Field	Apprentices, operating tables, test-subject escorts, specimen couriers
Strengths	Forbidden knowledge, body modification, seal dissolution, concealing sponsors
Weaknesses	Experiment runaway, ethical collapse, evidence left in the body

Hidden Hannya are not "people who want to become yoma." They dissect yoma, graft them onto humans, and read seals in reverse to push past human limits. When the Enryokan's philosophy of coexistence enters their hands, it becomes the language of control rather than understanding.

#Leadership and Structure

Tier	Key Figure	Role	How to Run
Leader	Akiyama Izen	Reverse sealing and yoma-core transplantation	Has him speak like a calm and kind physician
Enryokan heir	Ashikaga Shino	Interpreting old negotiation records	Use as an internal collaborator with a remaining conscience, or as a defector
Defrocked monk	Kakuren	Grudge and possession experiments	Justifies violence through religious language
Artisan sponsor	Kunimoto workshop head	Combining karakuri with Spirit Realm residue	Represents the face where money and technology feed research
Field apprentice	Hannya apprentices	Specimen retrieval, patient surveillance	Frame as young wrongdoers who can still be turned back

Akiyama Izen does not rave. He sincerely believes himself to be a physician. When a patient dies he says "failed case." When a test subject tears a person apart he says "rejection response." That coldness is the horror of Hidden Hannya.

#Faction Trait

[Aptitude] Reverse-Seal Knowledge (逆封知識)
Hidden Hannya researchers are more versed in reversing seals than in closing them. Barriers, Sacred Domains, yoma cores, and possessions are not patients to them — they are experimental formulas.
Effect: +1 to Wisdom checks relating to barriers, Sacred Domains, yoma cores, possession, oni transformation, fiend transformation, or reverse sealing. Increases to +2 if the check is aimed at weakening or dissolving a barrier or Sacred Domain effect.
If a PC acquires this: 1/combat, +2 to a defense or interpretation check against Incorporeal, onryo, or possession effects. After use, make an End check, Target Number 13 during the lull phase. On failure, -1 to the next check. The body retains traces of reverse sealing.
Applies to: Minion through Elite units and companion squads belonging to Hidden Hannya treat this as an innate trait. Lord-grade NPCs such as Akiyama Izen hold it in 1 General Trait slot.

#Companion Squads

All squads below apply Faction Trait [Aptitude] Reverse-Seal Knowledge.

#Hannya Apprentices — Minion

Scent: Young trainees who retrieve specimens and watch over patients in the back room of the clinic. They mimic their master's calm manner of speech, but their fingertips still tremble — a young evil for whom a path back still remains.

Wounds 1, Defense 12. Domination +2 (squad of 4).

Techniques:

Anesthetic Needle [Attack] — When commanded. 2d10 + Finesse(+1) >= Defense. Instead of 1 Wound, inflict -1 to the target's next check.
Specimen Retrieval [Kata] — When commanded. Place one incapacitated unit or yoma item into a carried state.

#Reverse-Seal Operating Table — Veteran

Scent: An operating crew that reads talismans backward and inverts seals to tear down Barriers. Under the pretext of treating a patient, they stitch human and yoma into a single body, and wherever they have worked an aftereffect remains.

Wounds 2, Defense 13. Domination +3 (squad of 3).

Techniques:

Seal Reversal [Kata] — When commanded. 2d10 + Wisdom(+2) >= 13. Weaken 1 barrier or Sacred Domain effect in the same zone for 1 breath.
Incomplete Oni Transformation [Upkeep] — During the lull phase, give 1 allied human squad +1 to its next attack. That squad suffers an aftereffect after combat.

#Leadership NPC: Akiyama Izen, the Reverse-Sealing Physician — Lord

Scent: The reverse-sealing physician who directs Hidden Hannya's forbidden experiments in the language of control. With a doctor's cold kindness rather than madness, he is the one who leads the apprentices and the operating table to treat people as material.

Akiyama Izen (秋山異膳) — Lord
Wounds 6, Defense 14, Energy 13
Courage+1, Finesse+3, Physique+3, Wisdom+4, Presence+1, Fate+1
Domination +2.5

Technique	Type	Energy	Check	Effect	Limit
Yoma-Core Transplant	[Kata]	4	—	Transform 1 human Minion or Veteran squad on the same battlefield into an oni-transformation test subject: Attack +1, Defense +1	1/combat
Reverse-Seal Needle	[Attack]	3	2d10+Wisdom >= Defense	[Incorporeal]. 1 Wound. If the target is under a barrier or Sacred Domain effect, additionally inflict -1 to the target's next check	—
Test-Subject Recovery	[Technique]	Reservation 2/Improvised 3	2d10+Finesse >= enemy attack	Negates hit. On success, may instead drop one adjacent test subject	—

Special:

Human Researcher: Izen is not a yoma. Exorcism alone will not end this — research records and test subjects must be handled.
Enryokan Contamination: If Enryokan remnant materials are on the battlefield, the first Reverse-Seal Needle check gains +1. Securing the materials first removes this bonus.
Faction Trait: Izen holds [Aptitude] Reverse-Seal Knowledge in 1 General Trait slot.

#Light and Shadow

Light	Shadow
Has the potential to treat victims of failed sealings and possessions	The boundary between treatment and experiment collapses
Enryokan heirs have preserved that knowledge	They use it as a tool of control and modification
Can save patients the shogunate has abandoned	The surviving patient may no longer be the same person
Understands the structure of yoma	Has no ethics to stop what has been understood

#As PC Affiliation

A PC belonging to Hidden Hannya is inherently dangerous. Unless the campaign is a villain campaign, it is better to frame the PC as a defector inside Hidden Hannya, a watchdog, a physician forced to cooperate, or an Enryokan heir. The appeal of this affiliation is not powerful forbidden knowledge — it is the temptation of "just this once, if I use it, I can save a life."

#As Primary Adversary

Hidden Hannya must show victims before the boss. Show the name the test subject had before becoming a monster, the reason the sponsor requested treatment, and how the Enryokan's records were distorted — and this organization becomes not a mere mad-scientist group but an evil that grew from Edo society's despair.

"Hidden Hannya does not believe in yoma. What it believes in is only its own hands — which can fix anything with blade and needle."