Niji, Lean on Me.

The story follows three members of the judo club. Niji Yamashiro is the female vice-president, Gaku is the president, and his friend Hiyori is a member. One day Hiyori asks Gaku, "Do you like Niji?," and Gaku promptly says he doesn't. Hiyori then responds, "OK then, is it OK if I confess to her?" Hiyori tells Gaku, "I'm going to confess to her. If you like her, you should come." Hiyori then approaches Niji after practice, and Gaku secretly spies on the exchange. On that spring night, one of these three will do something foolish that he will regret for the rest of his life. And he will never forgive himself for the rest of his life.

(Source: Anime News Network)

Note: Includes three extra chapters.