Usotsuki Mi-kun to Kowareta Ma-chan (Novel)

The setting is a rural city in which a kidnapping and a series of murders are happening simultaneously, where there was also a kidnapping eight years ago. The victims, the compulsive liar "Mi-kun" (the narrator), and "Ma-chan" (Misono Mayu) reunite and start living together, despite the fact that the kidnapped children were in Mayu's apartment...