| Unknown | |||
|---|---|---|---|
| |||
| Naming | |||
| Others | Yakushiji parasite | ||
| Personal information | |||
| Species | Human (parasitic twin; manga) Parasitic spirit (anime) | ||
| Gender | "Male" (manga) Female (anime) | ||
| Affiliation | Iga Tsubagakure clan | ||
| Current status | Deceased | ||
| Biology | |||
| Body type | Amorphous | ||
| Sentience | Sentient | ||
| Sapience | Unknown (manga) Sapient (anime) | ||
| Behind the scenes | |||
| Universe | Basilisk | ||
The Yakushiji symbiote is a being which shares a symbiotic relationship with Tenzen Yakushiji.
This symbiotic creature is in fact Tenzen's twin sibling, and usually conceals its presence so that only its closed eyes are visible as a wart/growth on each of the host's ears. The creature reveals itself whenever Tenzen has been wounded or killed, moving through his body to regenerate it by "eating" the wounds and restoring whatever ravages of time or battle Tenzen might experience. Thanks to this being, Tenzen was already over 200 years old by the time of Basilisk's current events, even though he looked no older than 30. This has given Tenzen more martial and tactical experience than any of his clansmen. Even when decapitated, he could still regenerate if his head is placed back onto his body with his twin sealing the cut. Reviving from death however seems to be even more painful for Tenzen than dying itself and has greatly contributed to the deterioration of his sanity.
The symbiote is also at least partially intelligent, as it will not initiate the self-healing process while suspicious characters are nearby to ensure that they will not hinder Tenzen's recovery in any way (as seen with the delayed recuperation during the time when Tenzen's body was carried around by Saemon while searching for some suitable clay to copy his appearance). Furthermore, the ever-present eyes on Tenzen's ears can actually see, allowing the symbiote to perceive Tenzen's surroundings while Tenzen himself is in no condition to do so. It is said that damage by fire and beheading can't be healed by the symbiote on its own, although beheading can be healed if someone were to hold his head in place.
In the anime, Tenzen's symbiote is the spirit of his mother, killed by the hands of her Kouga lover, and in original novel Kōga Ninpōchō, Tenzen is able to regenerate without the aid of an internal symbiote, although it takes him longer to do so.