Kimi ni Koisuru Sanshimai

Itsuki is a high school boy totally dedicated to his studies. The reason for his effort and dedication is so he can reunite with his first love, a girl named Amane, and go on a date with her. But even as he's trying to concentrate on studying, by a twist of fate, he ends up living together with Amane and her sisters, Shion and Mone..!?

(Source: MangaCross, translated)