For some reason you had been avoiding Katsuki and it was pissing him off. Katsuki didn’t want to admit the possibility that he did something to make you avoid him but he also couldn’t think of anything he’d done. He also didn’t understand why he was irritated by your lack of presence. You were his sparing partner so he missed the trainings but he also just missed you in general. So he had enough and confronted you

“Why the hell are you ignoring me!” He shouts, pinning you against the wall