Ain't it something? What makes that scene really funny is not only is Sukuna just standing there pondering, he's spacing out in the middle of a fight (where his opponents are there to defeat him) with one pair of arms crossed, hands on his hips and he's spacing out because he's trying to figure out why he's upset and what's his deal with Yuji, the same person who noticed he's spacing out.
He's not standing there coming up with some strategic plan of attack. No, he's thinking over his life choices and Yuji and why he finds him more annoying than anyone else and it turns out Yuji's unbreakable. Love to see it!!