第1話: 母に関する誤報を聞き、カイドウ・ハルは新しい兄弟であるレンに会うためにカナダへ旅立つ。

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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"... (Source: Crunchyroll)