Kotoamatsukami is the ultimate genjutsu granted by Shisui Uchiha’s Mangekyō Sharingan. The technique itself allows the user to enter the opponents mind and manipulate them by giving them false experiences, making it seem as if they were doing things on their own free will. It is regarded as a genjutsu of the highest class, due to the victim being entirely unaware that they are being manipulated.
As a testament to its high repute, the capability is strong enough to even negate Kabuto Yakushi‘s control over the revived Itachi Uchiha, in spite of the former’s authority being considered almost absolute. After the technique is used, it requires around a decade before it can be used again, but this period can be drastically reduced through the possession of Hashirama Senju‘s cells, as observed by Danzō Shimura‘s use.
Danzō gained access to this dōjutsu by taking and later implanting Shisui’s Sharingan into his own right eye-socket while Shisui was still alive. However, despite the additional stamina granted by Hashirama’s cells, Danzō asserted that he still couldn’t use the ability multiple times in a single day.
