Kou Mitsuki is a gamer of extraordinary skill who goes by Crim the Headhunter online. When he begins testing Destiny Unchain Online, the newest game from his father, along with a new device built to play it, the system turns out to be full of bugs. One of them changes Kou into a vampire girl. From there his life takes a sharp turn as he makes new friends and sets out with them to take on the game in an action fantasy adventure.