Ryu Hajime lives a normal life supporting his little sister and sick mother. However, when he is walking home with a childhood friend one night, the two run into a murder scene, where Ryu unintentionally kills the murderer in self defense with magic that he didn't know he had.

The next day, Ryu is visited by his grandmother who explains that his magic is actually familial magic that she also has. Ryu also learns that since he has killed a member of a decennial battle royale, he has now become a member of that battle royale.

Now, Ryu must fight in the royale, or risk his family, friends, or loved ones being killed by mages, assassins, or soldiers in the pursuit of personal glory.