Izuku was standing in the middle of a crowded train while holding close a wound on Katsuki’s side. How did this happen?

earlier Katsuki and Izuku had been in a fight with a villain who had a quirk that if introduced into a person’s bloodstream, would make them unable to think clearly at all and make them useless. So now they are stuck in a crowded train while Katsuki is bleeding and unable to process anything that’s happening