An epidemic of unknown origin strikes mankind, killing all adults and rendering the youngsters at the mercy of the vampire kind. Four years later, Yūichirō Hyakuya and his friends make a daring attempt to escape from the vampires, unaware that a mortal trap awaits them.

Four years after escaping, Yūichirō is part of the Japanese Army and is eager to become a member of their special vampire hunting force, the Moon Demon Company, but his reckless behavior leads him to be suspended, until a vampire attacks the local school prompting him to face the enemy against orders.