Master Sensei is the head teacher of the Yamanouchi Ninja School. He has many different skills and he has mastered Levitation and Astral Projection
He has instructed many ninja students:
- Yori, who befriended Ron Stoppable.
- Hirotaka, who was attending Middleton High School for a week during the whole student exchange program.
- Fukushima, who betrayed the school and allied himself with Monkey Fist. He was defeated by Ron Stoppable, who managed to channel the Mystical Monkey Power he received from the ancient monkey idols for the first time.