It all started when he was told he was quirkless, and with it came all the pain and hatred that has occurred to all other quirkless people before him.
When Izuku finally turned four, he was wondering what type of quirk he would get. "Would I get mom's quirk? Or will I get to breathe fire like dad?" The young Izuku wondered as he was going to the doctors to see what quirk he would get, not knowing what would have befallen him.