Daichi Kitaumekawa is Satou Matsuzaka's teacher who is renowned for his good looks and nice personality among his students. However, underneath this facade lies a deeply perverted man who takes an interest in Satou, obsessing over her after a school event. At school, Daichi is considered to be a kind and helpful teacher who demonstrates his concern for his students by speaking to them privately about personal matters and offering assistance in any way he can.

Spoiler

But in reality, he is a perverted man who wants to have a harem of women, regardless if they are his students. He tries to hit on his students a lot despite the fact that he has a wife and a young daughter.

Spoiler

Satou uses this fact against him as she knows that despite his cheating, he doesn't want to lose his family or take the blow to the reputation that would come if he were found out.

(Source: Happy Sugar Life Wiki)