Gosei Hatsumi

Gosei Hatsumi was a member of the Gosei Clan, who were once a noble samurai clan. The first-born son of the family is tasked with harboring the Gosei Spirit, a cumulative of the clan's entire teachings and memories. The Spirit is passed down from father to son, but Hatsumi's son, Kenji, has built a criminal empire in New York City and thus unworthy of The Spirit. Instead, Hatsumi was to pass on the Gosei Spirit to Kenji's son, Gosei Hattori. Hatsumi, on his death bed, reached out to Splinter on the astral plane, and asked if he could swap bodies with him so that he could pass this spirit to Hattori. Splinter agreed to help, even if it meant that he died along with Hatsumi's body should he pass during this time.

Hatsumi, as Splinter, directed the pre-teenaged Turtles to infiltrate Kenji's company, Goseico. Whilst there, Donatello and Raphael overheard to employees discussing the assassination of Kenji and Hattori. After they return to Hatsumi with this news, he orders them to kill the assassins. Unfortunately, the Turtles miss one of the killers, and he guns for Hatsumi. Kenji steps in the way and takes the bullets meant for his son as Leonardo stops the killer.

After convincing Hattori that the old rat did indeed contain the soul of his grandfather, Hatsumi transfers the Gosei Spirit and returns to his own body just in time for Hatsumi to pass away peacefully.