Chosen Hero

Hero (勇者) refers to the counter-part of Demon Lords, an existence that only those who have the blessing of a Greater Spirit of Light can obtain.

As is the case with Demon Lords, Heroes can be divided into those who are known as Hero in title or those who are Heroes as a "Class" as well as those who are neither or both.

Hero as a Class
Those who obtain the blessing of (or have a contract with) a Greater Spirit of Light have the opportunity to form a Hero's Egg within themselves and eventually "hatch" it and eventually become an awakened Hero. Hero's Egg is the equivalent of Demon Lord Seed and Awakened Hero is the equivalent of an Awakened/True Demon Lord.

Hero as a Title
Anyone can proclaim themselves a Hero, or be recognized by the masses as a Hero. In either case this "puts fate into motion" and causes this Hero by title to eventually have some sort of predestined connection with a Demon Lord that is unavoidable, though it does not necessarily have to be a hostile relationship.

Trivia

 * In the English translations Hero (勇者) is often mixed up with Champion (英雄) because both these terms are usually translated as "Hero" out-of-context. This has sometimes caused Champions in the English translation of the series to be mixed up with Heroes. Likewise the term Heroic King (英雄王) also refers to Champions and not Heroes.