Hayato doesn't know anything about Levi or the world he comes from. He's simply been carrying out his work as he does daily, and having this guy bust in for seemingly no reason isn't something he's going to let happen without blaming the guy. He certainly wasn't invited in to try and hit Hayato in the nuts.

"Tch-!" The guy got in his face, Hayato was going to bring him in closer.

Of course, he can't stay standing if Levi is yanking him to his knees. He blocks his face when the other bites at him and tumbles back, trying to keep the other from hitting him. Levi instead sits up, straddling him, and the Italian groans.

"Get off!"