Revolves around a seemingly loving family consisting of a kind father, beautiful mother, their first son Izumi and his younger brother Haru, the product of his mother's brutal rape by a criminal who is nonetheless raised as a normal member of the family--receiving the same love and attention shown to Izumi. When Izumi and Haru grow up, a serial arsonist begins setting fires and leaving behind puzzling graffiti on walls at the crime scenes. Izumi starts to unravel the mystery of the graffiti, with each location drawing him ever closer to the unexpected truth about genetics and the importance of family.