A housewife was killed by a falling fire extinguisher, which a boy of seven years dropped from the top floor of an apartment. The offender, however, was not accused because he was too young. Ten years later, a series of murders occur, which target young girls only. It is the boy accused of killing the housewife who comes up in the couse of investigation, while the son of the murdered mother is the witness of a new murder. When the two families of the offender and of the victim meet again, two opposite morals conflict with each other – one is to crack down on the sin beyond the law and another is to disapprove the retaliation.

Kazuya Naruse, an obedient programer falls for a girl "Rumi", whom he gets to know through chat rooms. Naruse lost himself in this love, as if he lives in another world. Rumi has a mentally ill husband. Spending time with these two, the illusion of love in Naruse gradually changes to uneasiness and insanity.