go ham w/ sexy headcanons: 2, 11-15 because i literally can't remember half of the specific numbers i want to ask between reading them and getting in your ask box lol
what is their romantic preference or inclination?
None. SKFNGKG Gaius. Wouldn't know romance if it hit him in the face, and if he did he would struggle with it. He is extremely close to the vest with his emotions and, as a result, isn't great at identifying them. To him, he isn't romantically inclined at all, because he isn't sure what that feels like to him.
He is likely just demiromantic. Parts and pieces don't matter. Mutual respect and patience is.
how do they feel about foreplay?
As a teen and fresh adult, he was absolutely not a man who would make sex worth his partner's time. It was a greedy, selfish act, a means to an end, a transaction of sorts. So long as he came and was distracted from The Horrors for a little while, he didn't really care if his partner orgasmed, was fucked uncomfortably raw, or enjoyed it at all. He was an asshole as a new recruit lol.
Once he hit his stride in the military and was no longer the youngest pup desperate to find a place - and, uh, his brain actually finished developing - his view began to change. He still was bad at foreplay, especially with partners he knew were one-offs, but he did make an attempt and was surprised how much better sex was when his partner was properly wined, dined, and lubed.
As a retiree, foreplay is a Requirement. He doesn't get hard at the drop of a hat anymore and generally uses the time as a gauge to see if he actually will get there. He is aware - and resigned - to the fact that sometimes penetration isn't an option with his ED, and has come to be quite proficient at getting his partner to orgasm in other ways. And, sometimes, getting them to do so is just the encouragement he needs to allow himself some enjoyment and a stable erection, and then he can encourage second out of them, too :-)
how do they feel about one-night stands?
They are the only sex he really knows outside of being with Midas. He isn't really sure how sex would be in a committed, exclusive relationship: even when he was with Midas, the engineer was still, on paper, married to his wife. Gaius had been perfectly fine being the young side piece, and it gave him enough freedom to still sleep around if he wanted.
He's fine with it. Exclusivity has never been something he feels worthy of or deserves, and "settling down" after retirement to provide Garlemald more soldiers had been a short-lived consideration as a 30-something. Even in most committed ships, I feel as if Gaius would, likely, accept if his partner sought out others while away from him. After all, he was young once, too.
are they openly flirtatious/sexual, or are they quite private?
I feel like this is tricky because he isn't horribly modest or conservative, but also keeps his emotions, desires, and wants behind about three combination locks and an armed guard. If someone else were to initiate it, he would likely attempt to return in kind, but in hushed ways.
HOWEVER, he also strikes me as the kind of man to put his hand on his partner's thigh under a tablecloth. Flirty, low stakes, low visibility. I think that's more his cup of tea at his current stage in life.
how open are they, or how do they feel about sexual experimentation? elaborate if needed.
At one point I think he was very much just "oral and penetrative sex only, thanks, good day" - again, sex was a means to an end and a way to let off steam. He was eating because he was hungry, not to enjoy the meal, so to speak.
He is open to experimenting with longer flings or friends-with-benefits situations. He won't bring out knives or breath play or being too rough unless his partner requests (or presents it) ahead of time. With more exclusive folks, I do think he is open to trying much, much more. HOWEVER, as mentioned earlier, I do think a certain level of trust and respect has to be met for him to agree to being the receiver/bottom/target/whatever you want to label it.
what is something they consider a kink of their own?
Probably bloodplay/knifeplay/breathplay, or cum eating. He once thought coming on his partner's body was well and good and sexy, but at some point he got to watch a partner lick his spend from their fingers after a handjob and it made him reconsider things.
(Also he would never ever ever admit it but there's something there about eating his partner out after coming in them / making out with them after they swallow / etc etc. And vice versa.)