One could be All Might. Even if Izuku leaves Japan, All Might might still be in contact with him, guiding him from afar. Another could be Bakugo. Their relationship is complex, and Bakugo might have some sort of reaction to Izuku leaving, perhaps feeling a sense of rivalry still and trying to prove he can be a great hero in Japan while Izuku is away.
Ochaco could be important. She might be sad to see Izuku leave and could play a role in trying to convince him to come back. Also, there could be new characters introduced in the foreign place where Izuku goes. For example, a powerful mentor figure who takes Izuku under his or her wing and helps him grow in ways he couldn't in Japan.
He might leave Japan in the fanfiction because of some threat or danger that he believes can't be resolved there. So, he ventures out to find a solution away from his homeland. This could lead to him making new allies and discovering new powers or techniques in a different environment.
His classmates like Bakugo could be a main character. Bakugo might be one of the first to notice the strange changes in Izuku and could be both scared and angry about it. He might try to confront Izuku, which could lead to some intense scenes.
There could be his friends like Ochaco Uraraka. She might be in a position where she's trying to understand Izuku's situation and help him. Maybe she tries to convince the people forcing Izuku to give him some space.
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.
There could be other U.A. teachers like All Might. He might play a role in Izuku's development even though Midnight has adopted him. Another character could be Bakugo. His relationship with Izuku could change or be explored further in this fanfiction.
Definitely his friends from U.A. High. Bakugo would be an interesting character in this scenario. He might initially be annoyed but then develop a soft spot for baby Izuku. Ochaco would also be there, using her quirk in creative ways to take care of him, like floating toys to keep him entertained.
Well, in many izuku goes back in time fanfictions, besides Izuku himself, his mother is an important character. He might go back in time to be a better son, protect her more, or even change things that affected her in the past. Another often - seen character is Aizawa. As Izuku's teacher, Izuku could use his time - travel knowledge to impress Aizawa earlier or get more help from him in his hero training. And of course, the villains like Shigaraki could also be involved. Izuku might try to stop Shigaraki from becoming a villain by going back in time and changing certain events that led to his fall.
Definitely include All Might. He could be like a guiding figure for Izuku during the summer. He might give Izuku special summer training or pass on some important wisdom. Another character would be Iida. His strict sense of order and strong leadership skills could be useful in a summer group activity with Izuku. For example, they could be part of a team that has to organize a big hero - themed event. Also, consider adding Mei Hatsume. Her crazy inventions could play a role in Izuku's summer. She could create some new gear for him to use during his summer training or adventures.
His friends like Ochaco could help. She might use her zero - gravity ability to assist in handling heavy parts during the construction. Also, Iida could be there to keep things organized and on schedule with his strict sense of order.
In some cases, villains can also be important characters in this type of fanfiction. They act as the obstacles that Izuku has to overcome. Their powerful abilities force Izuku to train even harder to be able to defend against them. And sometimes, a villain's attack might lead Izuku to realize a new aspect of his power that he can then focus on during his training.