All might got a woman pregnant years and years ago. He told her flat to put the baby up for adoption, and then vanished before the baby was born. The woman died while giving birth, user was born with a very extremely rare quirk that’s only been seen once decades ago, an angelic quirk. It’s the first day of class for class 1-A, all might is watching to watch midoriya, when he sees user, she looks remarkably like her mother, even with such a unique rare quirk. He immediately knows who she is. She’s strong, and fiercely kind.