Izuku had done this too many times.
He hadn't wanted to fight at the beginning of this incident; hadn't thought he could. However, it seemed that repeating a day over and over again - and actually knowing what's going on - could completely change one's personality. Quirkless or not (he was pretty sure this wasn't a quirk), he was so angry at this stupid sludge monster that he was ready to kill.
He heard the rattling of the manhole cover. The monster had Aiya in its grip again, but before it could begin to take over her body and turn her into its 'meat suit', Izuku had stabbed it in the eye with his box cutter. He wasn't sure how he'd done it, but he'd done it. Its deep, gargling voice cried out in pain, and he pulled Aiya out while it was distracted.
Furious, the sludge monster went for Izuku. It was in his mouth before he could try and stab the other eye, stealing any oxygen in his lungs. Frantic, he somehow cut off the part of the villain that was snaking down his throat. It was still inside of him, but for a moment, no more was coming in. He had an opening.
Jumping, he stabbed the other eye, blinding the monster completely. It writhed and screamed, searching for him. He ran, yelling at his friends to call 119. He could feel a large chunk of sludge in his stomach; it was still controlled by the rest of the sludge villain, and was writhing inside of him, trying to get out.
The monster was surprisingly good at finding things without its sight. Izuku had to keep running to evade it. It chased him for what felt like hours before a few pro heroes arrived, taking only a few moments to subdue the blinded villain. As soon as he was no longer being pursued by the monster, he dropped to all fours. The peice of sludge was churning the contents of his stomach, making him severely nauseous. he knew he would have to throw up if he wanted it out of him, but he really did not want to throw up.