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 don't have to worry about me. 
Go out and play.
Ren, mach dir wegen mir keine
Sorgen. Geh raus spielen.
No te preocupes por mí. Ve a jugar.
No te preocupes por mí. Ve a jugar.
Pas besoin de t’occuper de moi.
Non preoccuparti per me.
Vai pure fuori a giocare.
Não se preocupe comigo.
Pode ir brincar lá fora.