ちっちゃくてデカくて可愛いのに二股されてた七瀬さんを勘違い元カレから奪って幸せにする (Associated Names)

One day during his holiday, Yuusuke Ogami happens to witness his classmate, Nanase Hiyori, confronting her childhood friend, Kouma Yoshihide. In fact, the two had secretly been dating for a year, but during the same period, Yoshihide was also seeing another girl, essentially two-timing Hiyori. After being hit with the lowest of words from a…