Coy and self-conscious high school student Karin Karino never paid much attention to boys until she met Kiriya, a popular student from a nearby boys' school. Karin and Kiriya embark on a romantic journey despite Karin's classmate Yuka's best efforts to sabotage their relationship, but Karin soon learns that living happily ever after isn't on the curriculum when she becomes Kiriya's center of attention, as well as embittered Yuka's bull's-eye on her dartboard of hate.
Karin agrees to do another commercial shoot but is dismayed when she discovers that Shinji Takagi, Kiriya's object of jealousy, is directing the commercial. Meanwhile, Kiriya bumps into ex-girlfriend Saori Mikami at the studio, but he tells Karin he doesn't know her. The truth haunts Kiriya when Saori calls him while Karin is at his apartment. Can Karin deal with Kiriya's past?