Rui lost her parents in an accident when she was little, and had lived alone since then. She can't forget the mysterious boy who comforted her on the night of her parents wake. She started sending letters to him, the boy who she started calling Haru, even though she didn't know whether the letters would ever reach him. After Eisuke's apartment burns, he forcibly moves to Rui's apartment, which is bad, because Eisuke is a teacher in training at Rui's school. Thus starts their life together. Rui is very reluctant at first, but soon the time together becomes very precious to Rui. Buth then, they're discovered at school, and Eisuke leaves.
After two years, Rui is living with her aunt Akane and her husband. A boy, who looks remarkably like the mysterious boy from Rui's past moves next door. Rui has her hopes high, until he reveals to be Eisuke's cousin, Chiaki, and not Haru. When Rui starts high school, she starts to go out with Tarou. But then, she meets Eisuke again, and this time, he's a teacher at her high school. Rui's senpai, Chika introduces Eisuke as her fiance. When Rui receives a wedding invitation from them, she starts to notice her own feelings. She breaks up with Tarou, rushes into the church, confesses her love to Eisuke and kisses him, Chika sees them and breaks up with Eisuke.