The story follows Issei Hyōdō, a dim-witted, lecherous second-year high school student who is killed by a girl on his first date ever. Issei is reincarnated as a devil, and from that day forward, he serves as an underling of Riasu, a high-level devil who is also the prettiest girl on Issei's campus.
In four years' time the competition that will decide who the next Queen shall be will start. The strongest warrior will continue to rule the country according to tradition and expand it. The contestants need only be older than 12 years. They need not be human, intelligent or even of that country. The rules for the tournament are simple: murder is allowed. Any weapon can be chosen. The winner is decided when one of the participants flees or can't move anymore. The event is broadcast by the court's magic teacher through a crystal sphere to the whole population to see and enjoy.