Heroes (ヒーロー, Hīrō) are individuals who fight for justice against all evil in the world. They also protect innocent civilians from any harm against natural disasters, Mysterious Beings and Villains. Most heroes are registered in the Hero Association and divided into four classes, C-Class, B-Class, A-Class and S-Class, but the Rank 1 heroes of A, B, and C classes are substantially more powerful than the bottom ranked hero of the next class up; they chose to keep their Rank 1 position as a gatekeeper for reasons of their own.
Unregistered heroes are regarded as "weirdos" by the Hero Association and don't get any credits or mentions in any media.
C-Class (C級, C-kyū): is the lowest class out of the four classes. Although C-Class heroes are the weakest, in most cases their strength exceeds that of a normal person. When a hero enters the association, he begins here (unless he scores high enough in which case he directly climbs up to a different rank). C-Class heroes must perform weekly heroic acts or else they are kicked out of the association. The currently highest-ranked C-Class hero is Mumen Rider. There are currently about 390 heroes in this class. C-Class has the most heroes out of all the classes.
B-Class (B級, B-kyū): is the second weakest class. When a hero becomes #1 in C-Class, he or she can climb up to B-Class. Heroes in this class are stronger than the previous rank and do not have to perform weekly heroic acts. The currently highest-ranked B-Class hero is Blizzard of Hell. There are currently 101 heroes in this class.
A-Class (A級, A-kyū): is the second strongest class out of the four classes. When a hero reaches #1 of B-Class, he can climb up to A-Class. Heroes in this class are considered very powerful and are often the most popular heroes. The currently highest-ranked A-Class hero is Sweet Mask. There are currently 38 heroes in this class.
S-Class (S級, S-kyū): The highest class in the Hero Association. Here gather the most powerful heroes, who are said to be insanely strong, at least as much as an emergency army division. This class was originally created to gather individuals who, despite their low ranking, were capable of defeating Disaster Level Demon Mysterious Beings on their own. The currently highest-ranked S-Class hero is Blast. There are currently 17 heroes in this class. S-Class has the smallest number of heroes out of the four classes.