Bokura wa Itsu datte Tomawari o shite iru

Hina belongs to a girls' group centered on Karen, and Karen has Maki, an inconspicuous girl in her class, as her eye enemy. One day, Hina is talked to by a strange young man. She said, "I want you to help her (Maki)." From that day, changes begin to appear in Hina's heart.
(source: YouTube)