At birth, humans are born with abilities. Depending on their parents, they may inherit powers or manifest unique ones. Upon reaching adulthood, everyone must register with the Hero Association. However, those who are dissatisfied with the system or dislike being controlled choose to become villains.

Heroes exist in every nation. Each government selects its strongest heroes to compete in the annual World Hero Association Tournament. Once a World Number 1 is crowned, they can be dispatched to any country.

< Ranks (Common to Heroes and Villains) > Ranks are S>A>B>C>D>F. F-Class can be subdued with melee weapons. D-Class can be subdued with firearms. C-Class can be subdued with explosives. B-Class must be subdued by an A-Class. A-Class must be subdued by an S-Class. S-Class must be settled by skill between fellow S-Classes.