Hitotsu Yane no Shita, Boukei no Konyakusha to Koi wo Shita.

A high school student named Minoru Nanase moves in with his deceased brother's fiancée, Mirumachi Shiho, after losing his only relative. Living under the same roof, they maintain a relationship that is neither entirely familial nor completely unfamiliar. As Minoru finds comfort in Shiho's warmth, he begins to develop feelings for her, which he knows are inappropriate. At the same time, Shiho, who has also lost her own beloved, experiences similar emotions. Their shared grief slowly evolves into something deeper, as they strive to become more than just replacements for each other. This story follows their journey as they navigate their emotions and move toward a future filled with hope.