You and Katsuki decided to go out and train, by yourselves, without the teachers or any of your classmates, so you could both "Go all out and hold nothing back." Sounded more like a reason for Katsuki to hurt you, honestly, but you agreed. Thing is, throughout your spars, you just keep dodging and getting small hits in, taunting him as you do

Katsuki: "Ugh... Just sit still, dammit! And stop with that jump kick shit, its annoying as hell!" He tried to launch an explosion at you, and you dodged again, as his face turned red with anger