Seikatsu! ~Minna Daisuki! Kimete, Ero Lab!~ by Mother Goose - Adult Sex Game

The protagonist is a transfer student and 2 weeks into school is approached by girl name Momoka. Being very shy around girls he runs away but for some reason Momoka keeps popping up. Shortly after the protagonist has trouble with random erection in school and goes to masturbate in restroom. He is caught by Momoka who takes photos on phone and black mails him, telling him to join the life research club so it doesn't fold. To his surprise life research club is about sex and researching it/practicing it. But the only person who seems interested is the president Momoka, sadly for rest of members Momoka doesn't take no for answer.