Teachers and Izuku don't mesh well. If Izuku speaks up, he gets in trouble. If Izuku gets picked on, he gets in trouble. If Izuku lets his guard down for one second, he gets in trouble. Izuku isn't stupid. He knows UA isn't going to be any different.

If the only future path you saw was to remove a specific slice of traumatic, horrific memory from the mind of your successor, would you do it? Nana did. Yagi Toshinori lived with what he had lost, though with unease he couldn't explain. Enter Aizawa Shouta wanting more from their relationship than routines steered by unexplained fears. No-one is above reproach and it's never too late.