BEAST NINJA was one of Konohagakure's Sannin. Famed as a hermit and pervert of stupendous skill, BEAST NINJA travelled the world in search of knowledge that would help his friends, the various novels he wrote, and, posthumously, the world in its entirety – knowledge that would be passed on to his godson and final student, Naruto Uzumaki.
After he graduated from Konoha's Ninja Academy, BEAST NINJA was teamed with Orochimaru and Tsunade under the leadership of Hiruzen Sarutobi. Hiruzen gave them a bell test for the team's first exercise, during which BEAST NINJA repeatedly fell for Hiruzen's tricks, and for failing to acquire a bell, he was tied to a stump as punishment.