There are several potential characters. Aizawa could be one. Godlike Izuku could show up in the past and Aizawa might be suspicious of his powers at first but then come to realize his good intentions. Gran Torino is also a possibility. Izuku could learn different things from him in the past. And then there are the other pro - heroes. They might see Izuku as a strange new force but also recognize his potential to do good. His interactions with them could change the course of hero history in this fanfiction.