Hayari-kusuri (流行り薬) — a term for medicines and pharmaceutical preparations used in the field — refers to the category of plant-based and compound preparations documented in the shinobi primary sources for medical, operational, and combat applications.
Primary source evidence
The Bansenshūkai (万川集海, 1676) includes sections documenting preparations for wound treatment, endurance enhancement, and operational compounds. These reflect the self-sufficiency required of shinobi operating in extended field conditions without access to conventional medical support.
The knowledge base drew on the traditional East Asian pharmacological tradition as well as the botanical expertise associated with yamabushi mountain practice — a natural overlap given that the yamabushi disguise was one of the seven standard shinobi covers, and genuine expertise in the role’s knowledge base enhanced its effectiveness.
Categories of preparation
- Wound treatment: Styptic and antiseptic preparations for field use
- Endurance: The hyōrōgan (兵糧丸) — a concentrated food supplement with stimulant properties for extended operations
- Irritants: Compounds used in metsubushi-type devices for blinding and disorientation
- Sedatives: Preparations for subduing targets during capture operations (documented but details limited in primary sources)