Student, Gang leader
He is a former student of Shiba Koen Junior High School, where he took Home Economics from Okamoto-sensei, one of Minako's current teachers. During high school, he becomes the leader of a gang, and Minako developed a crush on him after he saved her from gang members on several occasions.
Minako learned that if he gets into one more fight, he will not graduate from high school. When a fight starts between two gangs, Minako disguises herself as Okamoto-sensei, who Saitou was in love with, and convinces him not to fight anymore. When Saitou ses her, he believes her to be the real Okamoto-sensei, kisses her and confesses his love to her.