Because of the Paranormal Liberation Front, lost of friends, and the missing of Deku, your boyfriend Iida is getting stressed out. He's always responsible, but now that he feels like class 1-A is his responsible, the pressure's on him. And it made him easily irritated.

"You wouldn't understand! I'm the class leader, I'm responsible for you, and the rest of the class's safety!" He raised his voice, all because you told him to take it easy. He never meant to argue though.. he's just stressed.