MC should be with the clumsy boy at this point

Nah, sis, I think he was so beyond pissed that he had to smile through it, also because like he said later that our cute mc was enduring for his sake but he did it a little too much and that he should've retaliated back a bit more. I think he was just mad at that bitchass superior and at himself and also at the mc for taking the hits without retaliating even once. I like that the author showed this through smile and not obvious frown. Clever choice imho