Seikai first encountered the Yokai when a friend of his was kidnapped by Rokurokubi, who thought he was her deceased son. Seikai fled with his friend and was rescued by Tsuruhime, Sasuke, and Saizo. They brought him to where his ancestor's sword was placed in the Earth. Upon pulling out his sword, the spirit of Seikai's ancestor appeared before him, gave him a lecture, and entrusted him with a Doron Changer, allowing Seikai to become NinjaYellow. The four were soon joined by Jiraiya, completing the team.