Hitotsu Toshiue de Ane no Tomodachi no Bijin Senpai wa Ore Dake wo Shinu Hodo Amayakasu.

Hina Airi is a senior and the most beautiful student in school. To Masahi Shuuma, she is merely his sister's friend, someone he only interacts with briefly and politely. After visiting her when she is sick, Hina starts acting differently toward him, offering homemade food, spending time together, and becoming increasingly familiar. She asks him personal questions and reveals a private side of herself. Their relationship quickly becomes more intimate, leading to a temporary romantic connection. Hina expresses a strong desire to become indispensable to him. The story follows this dynamic as it develops.