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 saw the cigarette burn marks 
on the soles of his feet, right?
Du hast die Brandwunden
unter seinen Füßen gesehen,
Viste las quemaduras de 
cigarrillo en sus pies, ¿no?
Viste las quemaduras de 
cigarrillo en sus pies, ¿no?
Tu as vu les cicatrices
de brûlures de cigarettes
Hai visto quelle bruciature di sigaretta
che ha sulla pianta dei piedi, vero?
Ele tinha marcas de queimadura
de cigarro na planta dos pés, não tinha?