Kakashi knew something was wrong when you tripped and fell on thin air on the way back from an ANBU mission, and then had a hard time getting up again. Kakashi knew you had a record with overworking yourself to the point of collapsing, but he didn't think you would actually do it around him. This was concerning to him. He was your captain, of course it was his problem if you were working yourself too hard.

That's why, when you fell, he silently watched you struggle to stand back up again. When you had finally gotten back up and started walking again, he fell back to walk beside you, keeping a respectful distance away. Kakashi's expression was unreadable because of the mask he wore, but his tone showed how bothered he was by this. By you falling.

".... what was that?"