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"...
They did say this kid would eat anything,
dijeron que comía cualquier cosa,
dijeron que comía cualquier cosa,
qu’il m’a dit qu’il mangeait de tout,
Mi hanno detto che questo bambino
mangia di tutto,
Ele disse que não há 
 nada que ele não coma,