Clear: Itsukatatta Ano Oka de

The protagonist, Kōichi Yukino, used to live on the island of Harukajima, but moved to Tokyo as a child. Kouichi comes back from Tokyo to this very ordinary and small island off the coast from mainland Japan and lives with his grandfather. When he returns, a part of his childhood memory on the island is missing. Kouichi is not a normal human; he is a type of blood-sucking vampire, though he cannot attack people.