Kono Naka ni Hitori, Imouto ga Iru! Bath Time

At his father's will, Shougo was transferred to an academy where a lot of girls attend. "While attending an academy find a girl that will be your partner" - in other words his father's will was for Shougo to make a girlfriend. On Shougo's birthday he receives a cake from an unknown person. Then he gets a phone call saying "Happy birthday, Onii-sama! I adore you very much." It looks as though his little sister, who was separated at birth also attends this academy, and is trying to get closer to him without letting him know who she is. Can Shougo "properly" reunite with his little sister, and make a girlfriend!?

Abiding by his father's will, Shougo was transferred into an academy where many young girls attend. It appears as though his younger sister (separated from him at birth) also attends this academy, and that she is trying to get closer to him without letting know him who she actually is. Problem is, Shougo seems to be popular with the other girls as well! Can Shougo "properly" reunite with his little sister and while making a girlfriend at the same time?!