When Kinzoku was younger, people didn't think his quirk was villainous. It was useful in helping people move things, retrieve things, protecting people, and he went through a Hero Course at school with no issues. He wasn't outstanding, but he was within the top percentages and managed to obtain his Hero licence without problem. He was a sidekick to a small-name hero for few years before seeming to vanish from the public eye.

He was young when he saw the fall of All Might, meaning he was growing up and attending school, aiming to be a hero in the years following as Japan tried to get back on it's feet. He saw how shaky things were and how the Popularity System shifted, as well as the rise of UA's Best (aka Class 1-A). He tried to imitate them, become a hero like people said he should be because he could help people. But until the populace recognised a new Symbol of Peace, crimes skyrocketted following All Might's Fall, and the influence of the League of Villains (regardless of if they were later defeated).

After being in the 'real world' following his graduation, and seeing the true world of Heroes for the first time, he found it hard to keep his ideals and morals as a hero. Some heroes were heroes still for fame and fortune and a Brand to sell, and there was still a drive for popularity and having an Image. This was emphasised by the fact all the rising stars at the time seemed to come from UA, meaning that lesser known heroes from other schools didn't get nearly as much limelight.

Kinzoku began to lose faith in heroes, instead following a moral gray area of doing what he wanted. Having a Quirk that could manipulate metal was very useful in an age where most things contained some components of metal. He could rob stores by just opening the doors. He started small, with no one noticing, until he just stopped caring about being a hero and did whatever he felt like. It escalated into full criminal activities, until he became an outright Villain.

He doesn't kill people unless necessary, believing it to be too much of a mess to deal with. He's much more like the yakuza/mafia, doing things for his own or his groups gain. He doesn't have a devious plan like corrupting everything or taking over the world at all, he just wants to stir things up, have fun, and do what he wants.

Black Iron is his licenced hero name, but he doesn't specifically use it as a villain. Once the media digs up who he is, they use his 'hero' name.