Meet Kokonoe Koumori. Vampire. King of the Night. Well, at least he was supposed to be, except for one flaw: he had always been too soft to even think about hurting the nightwalkers, let alone rule over them.

If he let his guard down, his family would be directly on the line—eyes are on the throne, and his family would not be spared. Currently, this included his mom, his dad, and his extremely annoyed little sister.

In the nights that blanket the sleepless Tokyo, under the wary eyes of the saints and mages and the anticipation of the nightwalkers, the young vampire must learn become a King fit for the mantle, because if he failed, then it's his family's life on the line. That said, though, how do you go about making a ruthless king out of a very kind young man?