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 I'm better, I'll make lunch for you again.
Sobald es mir wieder besser geht,
mach ich dir wieder eine Lunchbox!
Cuando esté mejor, 
volveré a hacerte el almuerzo.
Cuando esté mejor, 
volveré a hacerte el almuerzo.
Dès que je suis guéri,
je te prépare à manger.
Quando starò meglio
ti preparerò di nuovo il pranzo.
Assim que eu melhorar, prepararei
marmitas para você de novo, tá?