A teacher at Karukozaka High School, Otsuki quickly joins Hazama after he throws the school into Makai. He confronts the protagonist several times throughout the story. Each time he is defeated, he rebuilds himself in order to take the heroes down the next time. After the defeat of Chefei in the World of Greed, he steals the Ring of Kindness and tells the protagonist to come to his lab. He is faced one last time in his lab, where he finally meets his end. He is known for saying "there's no scientific proof that...".
Shin Megami Tensei: If... Hazama's Chapter
Otsuki is fought three times. The first is while the player controls Ideo Hazama. He bars Hazama entry to the gym in the night of the first day of the game. Otsuki was intrigued that Hazama could survive the demons invading the school even after being beaten by Akira Miyamoto and challenges him. His defeat gives the fifth doll to Hazama. The other two boss battles are identical to the battles in if....
