Eight years ago, Mochizuki Saya was raped and murdered by three juvenile delinquents. Protected under the Juvenile Act, the delinquents have been allowed to re-enter society... but Mochizuki Wataru, Saya's younger brother, hasn't forgotten their crime and wishes for their punishment.
Not long after his sister's death anniversary, he decides to look for those responsible, however, he is run over with a bike by one of the delinquents and hospitalized. While at the hospital, he awakes the ability to interact with other people's dreams and discovers that these interactions bring real-life effects. Knowing that his ability allows him to do a "perfect crime," he vows to avenge his sister... when night falls.