Meitara Juinjutsu

Koshiro's Juinjutsu are the cursed seals that were developed and spread by Koshiro.

Overview
Koshiro usually gives his cursed seals to his most powerful and unique followers and guinea pigs to either make them his strongest warriors or to prepare them to become a potential inheritors of his secrets. To apply a cursed seal, Koshiro usually palms his targets chest. This technique instantly stops the heart of his target. The seal then appears over the victims chest, where their heart is. The design of the seals vary from person-to-person as well as their inner power. If the victim had survived the application of the seal, they would awaken at midnight with the fullest form activated

Koshiro originally developed his seals through experimentation on Corpses, In which, after being reanimated could fight for extended periods of time without tiring or feeling pain. Koshiro created a seal which takes control of both brain and heart functions. Pushing them into a state between life and death. Similarly, there are various forms of the undead seals which grant various abilities. Those who have the seal also gains a compatibility with corpses, allowing them to literally assimilate missing flesh.

Mechanics
The seal forcefully shuts down heart and brain functions and takes control, leaving the user clinically dead yet still alive. Granting enhancements comparable to those of [Undead]. Koshiro's seal removes all physical limitations created by ones brains, increasing all physical attributes. The user must also possess an above-average chakra capacity in order to wield the cursed seal's power. What makes Koshiro's seals unique is that they can grant a form of agelessness and invulnerability, creating a warring demon that can fight for extended periods of time. Unlike Orochimaru's Juinjutsu which eats at chakra, Koshiro's seal does not eat the users chakra. This is due to Meitara Seals simply circulating chakra rather than converting. Although users lack a chakra boost, their physical capabilities are evolved exponentially. Some of the Undead abilities are also utilizied when not activated. Those who are infected are immune to disease, will age slower, and can constantly eat which will increase it's power. Because the seals forcibly shuts down it's users natural brain and heart, the seal it will kill the user when first applied. At midnight, their body will awaken and in a fit of rage destroy everything in their path until calmed and knocked unconscious. Additionally, when awoken, they will hold no memory of transforming. Prolonged usage of the seal gives Koshiro access to their chakra, allowing him the ability to influence their thoughts. His notes state of a perfect form which is a stuck state between life and death where the user is unable to die.

Transformations
The seals have a partial level and an awaken form. When inactive, the seal is simply a black tattoo on the user's body. Koshiro's seal have three parts, Brain(脳), Body(体), and Force(力). Each part regulates a certain aspect of existence. When partially activated, the Body Kanji glows as the affected body part loses color. Partial activation allows partial deaths of a user body which erases any natural physical limitations of that area. However, once receded, the User will feel any pain done. Awakened Form (復活, Fukkatsu; Literally meaning "Resurrection") of the seal causes the heart and brain to stop working. This is followed by many unnatural alterations of the user's body. Once transformed, common features shared include black eyes with white pupils, skin lightening or darkening, and thread markings appearing. When in this level, the seal also eats away at the mind and personality of its users, driving them to madness if used for too long. It also takes quite a toll on their body, since they are being mutated by the seal. The power of the cursed seal can even synchronise with the user's regular body with extended use, exponentially enhancing the abilities of their normal state. Users naturally become immune to diseases. It is this form which many strive to achieve. The brains natural limitations are shut off increasing physical capabilities to immense levels. Users no longer feel pain, require oxygen, food or water. Also, users can heal through other flesh which becomes their own once coming back to life. There lack of brain function makes them immune to Genjutsu.