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"...
If you like rice, maybe I'll make sushi rolls.
Si te gusta el arroz, 
puedo hacer rollos de sushi.
Si te gusta el arroz, 
puedo hacer rollos de sushi.
Si tu aimes le riz,
je te ferai des makis.
Se ti piace il riso,
ti posso preparare del sushi.
Já que você gosta de arroz, 
 acho que vou fazer sushi.