It takes a minute, and he's definitely pulling faces over this thing, but...eventually Kaiba eats the whole cupcake.

Because he is not letting Yuugi eat it and he means that with his whole fucking chest.

Once he's done though, he crosses his arms and stares Yuugi down.

You've had enough.

Besides: he'd already said he was going to eat it before Yuugi took his head off for his callous behavior. Nothing changed, other than Yuugi convincing him more strongly of what he would be doing here.

Besides which, you can't go anywhere. Whatever happens, you'll be party to it. I'd say I'm sorry, but I have a feeling you'd have eaten it if I didn't, out of some kind of idea of "protecting" me or something.

Ridiculous.