Kimi ni Koisuru Sanshimai

Kimi ni Koisuru Sanshimai summary:

In the world of daily full-throttle dedication to his studies, there's Itsuki, a high school boy. The reason he's putting in so much effort into his studies is to reunite with his first love, a girl named Amane, and go on a date with her. While he's immersed in these study-centric days, by a twist of fate, he ends up living together with Amane and her sisters, Shion and Mone..!?