Shiritsu Tantei Max ~Sennyuu!! Nazo no Joshikou~

Max is a private detective who is known - beside his investigative and combat skills - for his way with women. One day, he receives just the case he was hoping for: he has to travel to a remote space colony near the Sun - more precisely, to the women school in this colony. The principal of the school has committed suicide. Two agents that were sent to the colony disappeared under mysterious circumstances. It's time for Max to find out what's going on - an interesting side-quest to his main mission: have sex with as many girls as possible!

[From Moby Games]