"Sorry to have disappointed you," Kaiba says coldly. He's more annoyed at himself than Yuugi, but he always sounds like an asshole, so it might be hard to tell. "I think it's best to hold off for now, until I can give you a real challenge."

The words feel like acid on his tongue. He's admitting that he isn't at his best, after all. Which is, consequently, why he doesn't thank Yuugi for adjusting his pillow the rest of the way. That and...one other reason, which he's trying to keep off his mind.