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"...
You never even called me all those years!
Du hast mich in den ganzen
Jahren nicht einmal angerufen!
¡Hace años que no me llamas!
¡Hace años que no me llamas!
Après des années
sans aucune nouvelle.
In tutti questi anni non mi hai chiamato
neanche una volta!
Faz não sei quantos anos 
 que você nem me liga!