A plot could also revolve around a multiverse concept. In this scenario, Izuku from an alternate universe where things went horribly wrong is a villain. She might cross over into the main universe and cause chaos or try to change things to match her own world's situation. This allows for interesting character interactions and power dynamics as the regular characters have to deal with this different version of Izuku.
A more complex plot could involve a time - traveling aspect. Villain Izuku from the future travels back in time and meets a younger Tsuyu. He tries to manipulate events to his advantage, but Tsuyu's kind nature starts to change him. This could lead to a whole new timeline where Izuku's path to villainy is altered.
One idea could be that Izuku is kidnapped by a group who wants to use his knowledge of hero strategies against the heroes. They hold him hostage in an abandoned building. Another could be that a villain with a grudge against All Might kidnaps Izuku as a way to lure All Might into a trap. Maybe a group of anti - quirk fanatics take Izuku because they believe his powerful quirk is a threat to their cause.
One idea could be that they both enter a hero competition together. Female Izuku might use her intelligence and determination, while Katsuki's explosive power would also be a great asset. They could face challenges that test not only their individual hero skills but also their bond as siblings, like having to rescue each other from villains.
One plot idea could be that female Izuku and Shouto are paired up for a special hero training mission. They start off not getting along well because of their different approaches to heroics. Shouto is more by - the - book while Izuku is more instinctive. But as they face various challenges during the mission, they begin to understand and respect each other's methods, and a romantic bond starts to form.
Another plot could involve Izuku being part of a secret society of heroes with vampire quirks. They have their own set of rules and ethics regarding using their powers, and Izuku has to learn to navigate this new world while still aiming to be a regular hero.
Another interesting plot idea is that Izuku's quirk evolution is tied to his emotions. When he experiences strong positive emotions like hope or love, his quirk becomes stronger and evolves in unexpected ways. For instance, it could manifest as a healing ability in addition to his existing powers. This would make his character development more complex as he has to learn to manage his emotions not just for his own well - being but also for the sake of his quirk evolution.
Perhaps in the fanfiction, they are in a world where quirks don't exist yet. Baby Izuku and Shigaraki grow up in an orphanage. Izuku is always the one trying to cheer everyone up and bring people together. Shigaraki is more withdrawn but Izuku keeps trying to be his friend. As they grow older, events start to shape them in ways that are different from each other, leading to different paths that are still influenced by their early bond.
A possible plot could be centered around Izuku's struggle to control his Phoenix quirk. Since it's such a powerful and volatile quirk, he often loses control. This causes problems not only for him but also for his friends and the people around him. He then has to seek out an old, reclusive hero who once had a similar quirk to learn how to master it.
One idea could be that Izuku's time quirk allows him to reverse time for a short period during battles. So he can correct his mistakes and outwit his opponents. For example, if he made a wrong move in a fight against a villain, he could reverse a few seconds and choose a better strategy.
Perhaps the villain adopts Izuku out of a sense of pity at first. But then, realizing Izuku's quirk could be useful, he starts to use Izuku for his own gain. The story could involve Izuku being sent on dangerous missions by the villain. Izuku, being young and naive, initially obeys. But as he witnesses the harm his actions cause, he begins to resist. This could lead to a conflict between Izuku and the villain, with Izuku trying to find his true identity and purpose outside of the villain's control.