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"...
What if I catch your cold?
Was, wenn du mich
jetzt angesteckt hast?
¿Y si me contagias tu resfriado?
¿Y si me contagias tu resfriado?
Tu feras comment
si tu me refiles ta crève ?
E se mi prendessi il tuo raffreddore?
O que eu vou fazer 
 se você me passar gripe?!