“Mumen” is “without license” or “unlicensed”
The term “mumen” in Japanese means “without license” or “unlicensed”. It is the name of a character in the One Punch Man series who is depicted as a bicycle-riding hero who lacks advanced fighting skills but still works hard to protect others.
According to the official explanation book of One Punch Man, he originally rode a motorcycle, but repeated speed violations in order to hurry to crime scenes led to his license being revoked and he was forced to switch to a bicycle.
The name is derived from his characteristic and sense of justice.
By the way, he is the first rank hero in class C andz appears on the scene riding a mundane bicycle. (The bicycle called “mamachari (mama = mother, chari = bicycle)” in Japanese is a type of bicycle commonly used by housewives in Japanese for shopping and picking up their children.)