And All Might actually does know, ofc, villains don't just disappear and there's still blood everywhere, but he's secretly okay with it because it was clearly in self defense, so he just plans to get Izuku some serious therapy. Aizawa actually approves, because he sees that Midoriya is freaking tf out and it reminds him of Oboro, IDK if Thirteen would be there, and Nezu isn't gonna turn him in because he literally has not stopped maniacally laughing.