Arthur doesn't like change. As the crown prince, and therefore also future king, change is something he'll have to deal with. That doesn't mean he has to like it. So when he finally manages to get Merlin into his bed, after what has got to be the most ridiculous period of courtship in the history of mankind, Arthur spends quite some time being ambivalent about it. Because first of all, their dynamic understandably needs some time to re-adjust to the new element of their relationship. But it's more than that. Merlin changes everything.
Annoyingly, he doesn't even realize he's doing it, so Arthur can't even take it out on him, as much as he would dearly like to, without looking like a massive ass. Doesn't stop him from trying, though. But since there is now the added threat of missing out on the frankly amazing sex, Arthur only tries it once or twice. After that he gives up, and takes it out on the knights during training instead. Which also turns out to be a bad idea. Because after a few weeks of being smashed to bits every morning, Gwaine suddenly asks, with all the subtlety of a charging bull, if Merlin would just please put out already, so they can all have a little peace and quiet. This of course ends up being incredibly awkward for everyone involved, because to the best of Merlin's knowledge he has most certainly been putting out for a while now.
So in the end, Arthur is left to stew in his misery over how nothing is the same anymore. He'll get used to it eventually, of course he will, but in the meantime, he's being sour. Because while the changes in his routine are aggravating, they do come with the added bonus of kisses or quick tumbles at random moments. But the changes in himself are the ones which truly rub him the wrong way.
It could be the lack of physical affection while growing up, but Arthur doesn't normally like to hug. Or cuddle. Or spend any real length of time just touching someone else. But with Merlin he simply can't help himself. If Merlin is within arm's reach, Arthur has to touch him. Has to. It has become an imperative, rather than a chore.
What's worse is how his own body betrays him. Since the glorious moment in his teens when he'd figured out what sex was all about, he had been singularly goal-oriented in bed. Getting off was the target, no detours allowed. Of course he made sure his partner got there first, because that was just the courteous thing to do, but any time spent with company in his bed not actively getting off was pretty much considered time wasted. But with Merlin, Arthur suddenly found himself wishing he had more time to just be there. To just look, touch and taste for hours and hours. There was no end to his dismay when he realised one morning that they'd spent all night together naked, and hadn't even bothered getting off. And to make matters worse, he finds that he doesn't care. In fact, he's hoping they can do it again soon.
It's simply intolerable.
“You're in a mood again, aren't you?” Merlin sighs as he serves breakfast. Arthur has a sneering jibe all ready, but it never makes it out, because Merlin darts in for a quick kiss good morning, and after that, Arthur couldn't care less about breakfast. All he wants to do is kiss Merlin instead of eating. So because he's the prince, and because he can, he decides to do just that. Which is just added insult to his already injured self-image. Because kissing was never this interesting with anyone else. Kissing had been just one step of many on the way to getting off, along with holding hands, petting, stroking and so on. Arthur would go so far as to admit that he had been perhaps overly focused on his groin. But Merlin is just so... tempting. And not only in the ways Arthur expected.
He expected the temptation to drag Merlin into bed and have wild, enthusiastic sex at odd times. He expected the urge to get on his knees and drive Merlin crazy in the stables when returning from patrol. He expected the constant ache of arousal whenever Merlin is in the same room or even just on his mind.
What he didn't expect was how his lips tingled from just the thought of kissing his way down Merlin's neck, or how his hands twitched with the desire to reach out and touch, or how seeing Merlin's happy grin across the courtyard is enough to put a spring in his step.
Arthur pulls Merlin into his lap, ignoring the indignant squeak, and allows himself a self-satisfied smirk when Merlin melts against him after only a few seconds.
“So that's how it is,” Merlin murmurs against his lips, and Arthur nods.
“Yes, Merlin. That's how it is.”