Ten years ago, there was an accident during the transport of chemicals in the port city of Mizuho, as well as a series of murders, but it is now just a part of history. At that time, Izana suddenly became separated from her best friend Tetsuo, and she never could come to terms with his disappearance.

This summer Tetsuo suddenly reappeared before the overjoyed Izana. However, he revealed to her a terrible truth…