Sunset Free Birds

AU idea where they became vigilantes that ended up in jail a escaped to be with each other.

In this AU, Momo's parents are selfish, rich snobs, but she became disillusioned by them as a result of watching heroes, real selfless people. They don't allow her to apply for hero school and she runs away from home to become a vigilante since becoming a hero is impossible without them finding out.

She meets fellow vigilante, Sato, who (in this AU) failed the Entrance Exams but aspires to be a hero from his impatience to save people with his Quirk. He has to go into disguise since hero work without a license is illegal.

One of their exploits leads to them unintentionally getting civilians killed as a result of obscuring heroes, just like Gentle Criminal's mistake. Wrecked with guilt, they turn themselves in peacefully. Momo's parents disown her (not that she would want to owe them anything) and Sato asks for his parents to not spend their hard-earned money to try (most likely fail) to bail him out. Being separated from each other and surrounded by real criminals drives them to escape prison thanks to Momo's beautiful mind and go off the grid to spend their days in solitude.

The story of two rejects of society: a reject of the humble and a reject of the nobles.