If it hasn't been done yet, someone should write a fic called "Post-Duel Clarity" wherein Kaiba and Jounouchi end up making out and rutting up against each other in a broom closet after a duel for the first time, and right after they come down from their orgasm they're immediately like "oh FUCK why did we do that?!?!?" and panic/flee the scene.
Only later when they're back at their respective homes they keep tossing and turning unable to sleep because they're still thinking about the encounter-- how good it felt, how they just sort of clicked and fell into the motions naturally once things got going. They start reconciling the fact that, yeah, alright, the other is attractive... physically, anyway. Personality was a separate issue entirely...
But then again... even though it all began with their usual barbs, pleasure overrode their verbal spat effortlessly. None of those empty threats/insults really mattered. What mattered were those tender touches, hands that ignited fires wherever they wandered, and how in sync they were. As they rocked together they created this intoxicating ebb and flow that didn't need any words. They didn't know they could have this sort of chemistry with someone from right out the gate-- much less with them. It was both terrifying and thrilling to recall...
Naturally, unable to sleep, Jounouchi would probably eventually muster up the courage to text Kaiba some basic "you up?" type of message (lord knows Kaiba's pride wouldn't allow him to say anything first.) After a brief beat of hesitation, Kaiba jumps right ahead to calling the blond in a brazen attempt to wrestle some control over the thoughts swirling in his head. After all, he performs best under pressure, right?
Jounouchi: ... I wanna know what you're thinking about.
Kaiba: I'm thinking about hanging up and blocking you.
Jounouchi: Mm... was having trouble sleeping, you can guess as to why. And it seems to me like you're having the same issue.
Kaiba: I am not going to talk about--
Jounouchi: -- Good. I'm not ready to talk about it either.
Kaiba: Then why the hell did you contact me in the middle of the night?!
Jounouchi: Told ya already. I'm having trouble sleeping.
Kaiba: And? What do you expect me to do about that??
Jounouchi: You can't sleep either. I figured we could... help each other out?
Kaiba: ... Over the phone.
Kaiba: You're a freak, you know that?... mangy mutt...
Jounouchi: I'm not hearing a 'no'.
Cue them masturbating to the sound of each other coming undone. (Which leads to yet another spiral of "what are we DOING?" questions post-nut lol... and so the cycle continues until the finally can admit they work really well.)