He can handle being the butt of the joke this time around if it makes Prom feel better. The smack gets a dramatic response, grunting and holding first his arm then pressing his hand over his heart. "Oooh ouch" But he's grinning, laughing it off and reaching out for Ignis' hand.

If he realized Prompto thought there was even a chance that he'd cheat on Ignis he'd have been horrified, hurt and a little betrayed. He would never do anything to hurt Iggy. Not in a million years. But he was always a little flirty and handsy when he'd been drinking, they all knew that. It would never ever go beyond that.

"Yeah, he's right. Luckiest guy in the world." Hope you were prepared for that to lead into gross cuteness, Prom, because he actually brings Iggy's hand up and kisses his knuckles before tugging him close enough to put an arm around him.