サマータイムレンダ

Two years after leaving for Tokyo, Shinpei Ajiro returns to his home island of Hitogashima for the funeral of Ushio Kofune, the childhood friend who drowned saving a girl. When he learns of strangle marks on Ushio's neck, Shinpei suspects her death was no accident. His search soon collides with the Shadows, doppelgangers that copy a person's appearance and memories before killing and replacing them. Each time Shinpei dies, he wakes again on the day of his arrival, replaying the same days to uncover what is hunting the island.