Kaiba in another situation might have reacted differently to loss. He wasn't fond of losing, but he'd long since learned to accept it when it happened, and fixate on achieving victory in the future to settle the matter.

That's not what he does this time.

This time, when Yuugi takes him out, Kaiba slams his hands on the table, scattering the cards everywhere and letting out a frustrated snarl.

"Again!" he snaps, his eyes wide and practically vibrating. "I won't lose to you again!"

...Yeah he's not okay.