Having come to Canada upon hearing the fake news that his mother Haruko is in critical condition, high school student Kaidou Haru meets a young boy named Ren. Haru is forced to spend the summer with Ren. Every day is a battle.

Brothers Aki and Shima are upset by the sudden appearance of a "fourth brother" in the Kaidou family, and Haru's excessively affectionate attitude towards Ren makes Aki explode with rage. Meanwhile, Haru happens to witness a car accident in the city.

Spring arrives, and Haru's dream of living with his brothers finally comes true. They move into a house together, and with the help of his former coworker Ikuyoshi, Haru's plans to open a cafe seem to be coming along as well.

Just when Ren begins attending school, he's seen kissing Haru goodbye by his classmate who is curious about their relationship.

While Haru and Ren are out at a nearby zoo, Aki calls Haru to let him know a woman calling herself "Kiyoka" has showed up at the house. Kiyoka is Haru's high school classmate and the co-owner of the cafe they're about to open.

Ren manages his school life with the help of his classmates, but he collapses during a PE class.

Haru's cafe "WHITE FANG" begins flourishing immediately after it opens. Even Haru and Ren's recently awkward relationship is getting back to normal. However, Aki is in a terrible mood.

Haru suddenly awakens to the sound of rain in his room. Shaken by the sight of Ren in his dream, his breathing becomes erratic. Realizing the reason for his dream, the next morning Haru questions Ikuyoshi.

The e-mail Ren sent prompts Haruko to come to Japan all the way from Switzerland. Eagerly looking forward to seeing Haruko again, Ren innocently bubbles with excitement. What will happen to the brothers' quiet life?!