Sister☆Boy

Your parents are going to leave you behind due to their work. You are Shun Miyama. You find out about this one day before their departure, and you also find out that they have already picked out your school and a place to live. You are waiting for Kasumi Sagara, a girl from your apartment to pick you up, but you feel strange. Well, guess what...

The apartment you're going to be staying in is restricted to girls. They think you're a girl! Since you were little, people have always mistaken you as a girl. However, you're all man inside; face it, you're in heaven now!!

[From Gamelex]