Whats about the boys reaction when their s.o suddenly hug them from behind or give them a kiss out of the blue and say that It was just because they wanted it?

How adorable!

Noctis:

This boy needs a lot of mental preparation for any display of affection. He likes to pretend he’s very unflappable. But something like this would knock him off kilter. Like, he’d be a blushing stuttering mess with a kiss. Perhaps he’d just blush with a hug, and wrap his arms around them in a knee jerk reaction. 

“What was that for?” He’d ask. And when they’d give their answer, he’d definitely have to hide his face. He wouldn’t be used to just…affection out of the blue. (But he’d love them for it and hope they’d do it more often.)

Prompto:

He wouldn’t even question it honestly. He loves contact with his S/O, they love contact with him, it’s a win win situation. Though the first time they do it he’d be a bit flustered. Like, what did he do to bring this on? Upon getting his answer, he’d realize that, Oh MY GOSH, WE’RE DATING AND I’M ALLOWED TO SURPRISE THEM TOO. 

This often dissolves into them both trying to one up the other. (Though nothing tops the time he kissed them right smack in the middle of a fight, took a selfie while doing it, and then sprung back into battle like nothing happened.)

Gladiolus:

For him, it’d mean more. He’d return whatever they gave him on reflex, only realizing it happened after it was over. Asking them would only lead to that vague answer of they felt like it, but he’d worry that there was another reason. But that wouldn’t stop him from also surprising them too. 

And honestly, if his S/O did it in front of the others, part of him would be pleased. It’d mean they weren’t afraid of others seeing how much they cared for each other. No hiding their affection in this relationship would make him a damn happy man.

Ignis:

He wouldn’t really ask questions, perhaps too flustered by their actions. He’s someone who’s used to things being planned out, or perhaps he’s the one who usually initiates all contact. So them surprising him would REALLY be a surprise. But not an unpleasant one. He’d find that he’d look forward to a random hug, and he wouldn’t be very opposed to an unplanned kiss….

So long as the others didn’t tease him too much.