Mukashi no Otoko Tomodachi to Doukyo wo Hajimetara, Jitsu wa Bishoujo Datta: Kyori-kan ga Ano Koro no Mama de Chikasugiru

"Kei-chan, see you tomorrow!" — That promise was never fulfilled, and young Kirishima Keisuke was separated from his only close male friend, Maa-chan. Then, ten years later, the person who arrived due to their parents' remarriage was none other than Maa-chan—now Masaki—who had grown into a charming...

Source: MyAnimeList