Keiyaku

Keiyaku (契約, Contract), known alternatively as Blood Pact (血協定, Chikyōtei), are powerful covenants between two parties used for various purposes; it could be enslavement, empowerment, or a mutually beneficial symbiosis. The Battle Doll technology, at its core, utilized a very potent form of Keiyaku, as did the Shirushi favoured by Shinzō.

Types

 * Saiaku no Keiyaku (最悪の契約, Hellish Contract lit. The Worst Contract) -- a form of contract employed by the, which is bestowed upon those they consider worthy. It allows the one affected to enter a Skull-Clad Form (頭蓋覆い, Zugaiooi) which is achieved when the Kushanāda pool their reiatsu into a single individual.


 * Kitanai no Keiyaku (汚いの契約, Beastly Contract lit. Unclean Contract) -- a permanent contract postulated by Kei Yume to be an unintended irregularity in the Reincarnation Cycle, which gave rise to the Fōrun-juu. The latter group of s gain their power from various animals, an example being Riki Nagakura whose animal is a wolf.