All Might would probably be in it. Since he's Izuku's mentor, he could play a role in helping Izuku understand and control his time - controlling power. Maybe he has some past experience related to time powers that he shares with Izuku.
In this 'izuku controls time fanfiction', perhaps he discovers his time - controlling power accidentally. He then uses it to explore different timelines. He might meet alternate versions of himself and his friends. This exploration of different realities could lead to him finding a way to make his own timeline a better place, like bringing back fallen heroes or preventing the destruction of parts of the city.
Ochaco Uraraka could also be a common pairing. Since she has her own insecurities and dreams in the hero world, Izuku's reality - controlling power could play a role in either helping her achieve her goals or creating new challenges for their relationship. For example, if Izuku accidentally changes something in reality that affects her family's financial situation, it could impact their relationship and how they interact.
One interesting plotline could be Izuku using his reality - controlling powers to create a world where everyone has equal opportunities in the hero world, regardless of their quirks or background. He might rewrite the rules of hero society to make it more inclusive and fair.
All Might often appears. Since he was Izuku's mentor, in time travel scenarios, he might be the one Izuku turns to for advice or assistance. Another common character is Bakugo. Their complex relationship can be explored further in time travel stories, like if Izuku goes back in time, he might try to change how Bakugo treated him in the past.
Bakugo is often paired with Izuku. Their relationship is complex in the original series, and in fanfiction with Izuku's time quirk, it could add more depth. Bakugo might be jealous of Izuku's new power at first but then come to respect it as they face challenges together.
Well, Harry Potter himself is surely one of the main characters as the title implies he has the power to control time. Hermione Granger is likely to be another main character. She is always by Harry's side in the original series and would be there to help him understand and manage his new time - controlling ability, perhaps with her vast knowledge and logical thinking.
One possibility is that Percy uses his time - controlling ability to prevent a great disaster in his world. Maybe he goes back in time to stop an evil force from being unleashed in the first place.
One common character paired with Izuku is Ochaco. Their relationship could be further explored in the context of Izuku's time - control ability. Maybe Ochaco helps Izuku understand the moral implications of changing time.
Bakugo is often paired with Izuku in izuku time skip fanfiction. Their relationship, which was initially one of rivalry, can develop into a more complex and collaborative partnership over the time skip. They might learn from each other's strengths and work together to face powerful villains.