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"...
Fumie and I drop by to check 
on her once every three days.
Fumie und ich kommen alle 3 Tage vorbei,
um nach ihr zu sehen.
Fumie y yo vamos a verla cada tercer día.
Fumie y yo vamos a verla cada tercer día.
Je vais la voir avec Fumie
tous les trois jours.
Fumie e io passiamo a vedere
come sta ogni tre giorni.
Eu e a Fumie vamos lá para 
 vê-la uma vez a cada três dias.