Traversing the cities of Berlin, Seoul, and Tokyo, a 10-year-long love story between two young men is told. It all starts when Ryu Narutaki, who left everything behind in Japan, is saved by a boxer named Johan Hwang in a foreign land.
Set on mysterious Kaiden Island where abandoned people arrive. Nanakusa and Yuu Manabe were childhood friends. Now, they are high school students and they meet again on Kaidan Island. They get involved in various cases.