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"...
To be honest, I don't really want 
to remember my life with her.
Eigentlich erinnere ich mich an das Leben
mit dieser Mutter nur ungern zurück.
La verdad, preferiría no
 recordar mi vida con ella…
La verdad, preferiría no
 recordar mi vida con ella...
Honnêtement,
In tutta onestà, non ho voglia
di ricordarmi com'era vivere con lei...
Para ser sincero, não quero me lembrar muito
de como era conviver com aquela mãe.