The Detective Is Already Dead, Vol. 8 by nigozyu
Kimihiko Kimizuka was once the assistant to two ace detectives, and after achieving a miracle, the sequel was ordinary life. The Ritual of Sacred Return was supposed to be the moment world peace was achievedbut instead, it was discovered that this was a product of false memories. As the search for the truth begins, it seems the memories of another Tuner, Rill, may hold the key...