Todoroki revealed his backstory to Mii/Kyouma Hououin
Todoroki at one point in his past, had a lone confrontation with mii after he kept getting bothered by her similar to what happened to Kaede in chapter 5, at some point she made a statement about how he probably doesn’t use his fire because of a sense of Superiority, after that he hits his breaking point and revealed his past to her, Which immediately caused her to burst into tears revealing her true personality to him as she frantically apologized to him, stating he hates her because she reminds him of endeavor, which he awkwardly had to reassure her that he doesn’t hate her. At one point Todoroki asked Mii if she was his illegitimate sister
Considering what he said to Deku in canon and Kaede in this fic when she revealed her Hawk Wings, it’s a very high possibility.