Usotsuki Mi-kun to Kowareta Ma-chan: Totteoki no Uso

The setting is a rural city in which kidnapping and series of murders are happening simultaneously. Eight years ago, a boy and a girl were kidnapped and suffered through the hands of their perpetrator. The victims, the compulsive liar "Mii-kun" (the narrator), and "Maa-chan" (Misono Mayu) reunite and start living together, despite the fact that the recently reported missing children were within Mayu's apartment…

adapted from the novel series of the same name