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 is this freezing cold development?
Wie konnte es auf einmal
so kalt um mich herum werden?
¿Por qué esa aura tan fría?
¿Por qué esa aura tan fría?
J’ai l’impression 
que mon sang s’est glacé…
Perché gli eventi hanno preso
questa piega agghiacciante?
Mas que reviravolta foi essa?!