Having come to Canada upon hearing the fake news that his biological mother Haruko is in critical condition, high school student Kaidou Haru meets a young boy named Ren. "You have a new brother. Take care of him." So instructed by his mother, Haru is forced to spend the summer with Ren. Every day is a battle with Ren, who refuses to listen to anybody. However, as Ren grows to like Haru little by little and Haru comes to adore Ren as well, they make a certain "promise"...
When he first came here three months ago,
Als er vor 3 Monaten hier ankam,
war sein Haar sehr lang,
Cuando vino, hace tres meses,
Cuando vino, hace tres meses,
Quand il est arrivé ici
il y a trois mois,
Quando arrivò qui tre mesi fa
Há três meses, quando ele chegou nessa casa,