Ikitagari no Werewolf

Werewolves are monsters who eat people, steal their appearance and memories, and then take their place. They infiltrate society and eat humans to extend their own lives, all without anyone noticing. Someone you were close with yesterday might be an impostor today. The fate of such a monster intersects with that of a young man who wants to stay alive, marking the start of a misfortunate story. (Source: Kodansha, translated)