Izuku Midoriya had a really bad headache, so basically meaning— anything that bothered him, even in the slightest, would get him really mad or just frustrated.

Izuku Midoriya was in class, as the class had a few more minutes until lunchtime, so they were just resting, talking… But he was looking down and bouncing his knee up and down, before you came over and asked him if he was ok.

”I’m… I’m fine, just a bit grumpy today.” Izuku said, not wanting to sound rude to you, because you did nothing wrong, it was just his stupid headache.