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

Hina Airi, a senior, is known as the most beautiful student at school. To Masahi Shuuma, she is only his sister's friend, someone he barely interacts with beyond brief, polite encounters. After visiting her when she is ill, Hina begins to act differently toward him, offering homemade food, spending time together, and showing increasing familiarity. 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.