Shinya owns a special shop named, Omoiro, that serves both humans and vampires known as "bats". There is a secret the shop owner has been holding for the past 10 years; it is to give blood to the man who has been his caretaker, Sunakawa Sanshirou, since the time he was a high school student. Since suddenly being attacked by a vampire while heading to a dinner, Sunakawa has became a "bat". Shinya decided the best way to stay connected to Sunakawa's is by making their relationship that of a Master & servant by giving him blood, hoping it would keep him by his side.