Prequel, back during the Wutai War. Zack gives Sephiroth the Talk. No, not THAT talk.
"I'm Gongagan," Zack told him one day as they sat on a rocky ledge above the camp. The two of them were up on the cliff, close enough to notice any panic amongst the troops but out of range to be called back for some urgent whatever that Sephiroth or his Second in Command ought to supervise.
They'd been fighting a war together in Wutai for the last three years. Sephiroth added to Zack's file regularly. Zack mentioned things he'd done as a child or teenager every time they socialized with the other SOLDIERs (often via getting drunk.) Zack's origins weren't exactly newsworthy. "...Yes?" Sephiroth replied, doubtful, an eyebrow arched.
Zack sighed, making the kind of grimace Sephiroth had learned to label 'uncomfortable'. It wasn't one he was used to seeing on Zack's face, though. "No, I mean, I'm really Gongagan." A long, searching look at Sephiroth's face, his eyes. "You haven't heard about that one, huh."
"You mean another 'you know what they say about...'? No."
Zack's eyes slid blindly over the jungle, lips moving without sound as if trying out arguments in his head. And then, abrupt, he chose one. "Gongaga has legal polygamous marriage."
It was ... close to what Sephiroth had expected - most of the jokes his Firsts made that came linked to Zack's origins were about his sexual proclivities. Yet so different that he kept still, silent. What he knew about legalized relationships could have been taken straight from the dictionary; there was no personal experience, no emotional content to react from, but Sephiroth wasn't so far removed from civilian life as to not know it was... unusual.
"... One person can have several wives. Or husbands." Zack leaned back on his hands in a show of casual relaxation belied by his tense shoulders, swung his legs in the void, heels rapping against the rock. "Not my parents, my parents were really mono like that - even in Gongaga most people are - but I had an uncle who had three wives and a husband, and two of his wives also had this one other guy... nevermind."
"You've met someone else," Sephiroth replied, because lack of experience didn't mean stupidity.
He wasn't sure how he felt about that. One thing he could take from the rambling was that Zack wasn't telling him he wanted to end things between them. But...
"Are we even more than casual?"
They were friends, he knew that, accepted it. (Was grateful for it.) But both of them had other ... shower handjob buddies, as Zack called them. Sephiroth had gathered from the men's behavior that those didn't count. (Didn't, actually, even officially exist outside of the shower room.)
"Seph, I'm telling you because I want us to be more than casual. Because I think - you and I, I like that. We work pretty well, huh?" A tentative smile. "I want to keep that up, as long as possible. But I'm - heh, I'm Gongagan that way. Someday I might meet someone else; not to replace you but... alongside you." His voice had gone quiet by now, serious. "I need to know if it's gonna be a dealbreaker."
"If it is?" he asked, more academically curious than anything else.
Zack must have heard it in his voice, because he relaxed, though Sephiroth could still see residual tension in his shoulders. "We stop feeling each other up, I guess. I don't need to get any more attached than I already am," he added with a chuckle that didn't manage to make it sound in any way like a joke.
Sephiroth watched him in silence, trying to discern whether he was surprised. No, he really wasn't. He'd... he'd known, he'd perceived - felt - it before. That he was special to Zack. Hearing the words was unexpectedly pleasant, though.
"To be honest, I don't know. What you do with the other Firsts doesn't bother me..."
"Yeah, I'm thinking I kinda want to cut down on that, actually."
Zack shrugged. "It's one thing when we're at war and stressed out. Everyone needs to relax when we get back to base. But the closer we get to going home, the more twitchy the straight guys in the unit get about trying to figure out if they've accidentally caught the gay and whether the other guy is gonna want to date once they're all home and closer to their potential girlfriends."
Sephiroth frowned slightly as he worked through the implications of that. "That does seem one-sided."
"Eh. Not really. I have zero interest in any of them as more than buddies. You're... You're more, you know that, right?"
"Ah." When Sephiroth smiled it came out small and strangely lopsided, nothing like any smile he'd ever given. "I gathered. Would you want me to cut back as well?"
Zack's answering grin was about a terawatt brighter. "Aw. Man, the other guys would hate me."
Sephiroth let out a snort. Somehow he was still smiling.
"Naw," Zack drawled, somehow angling the swing of his foot so it brushed against Sephiroth's. "I'm basically jealousy impaired, so whatever makes you happier."
Sephiroth angled his toes out, hooking Zack's foot behind the heel as it swung back. "Noted. The question is, am I."
He looked down at their feet, Zack's mud-splattered, steel-toed boot and his black leather one; made Zack's foot bounce once or twice tentatively. Hm. The gesture itself was pointless, silly. That Zack allowed it, complacent, personal space wide open to Sephiroth... It made him feel good. Special. He thought he might touch Zack just about anywhere right now - the top of his head, his elbow, his shoulder blade, heh, even his nose, and he would allow it without having to tense and pause and decide the offense wasn't big enough to retaliate, to break contact. Unrestrained access. (Trust.)
Someone else being allowed the same liberties...
"I'm sorry. I can't begin to imagine how I'll react." Frowning, he looked down at the busy tents in the clearing underneath. "Logically there should be no reason why that would be a problem, but this isn't ..."
"Yeah, it doesn't work like that," Zack agreed quietly.
"We can make the attempt," Sephiroth was saying without a second's delay, suddenly tense at the thought that Zack might decide to take it back. "If I can't manage," if he couldn't, if some unknown emotion roared up from unexplored depths, protested... He finished, stiffly, awkwardly, words inadequate, "I would still like to be your friend. I," a pause, looking for better words, but nothing wanted to come. "I will - always. Want to be your friend."
Zack gave a slow, thoughtful nod. Nudged his foot so Sephiroth looked up at him. He didn't smile.
"I won't leave you. Whatever happens, promise, I'll be there."
They didn't say anything else for a long minute, just looked at each other, with that strange, intense atmosphere between them.
Of course Zack broke it first.
"So... Status changed to 'casual access restricted, authorized personnel only'?"
Sephiroth stared at him for a second longer, and then pursed his mouth sternly rather than let himself smile. He had a feeling Zack wasn't buying it, though. "... They were right, you are a dork. Shall I ask Rufus for the appropriate paperwork for a corporate merger, Lieutenant Fair?"
"Oh god." Zack burst out laughing. "Like you can talk, you dork squared!"
He was still laughing when he leaned in and kissed Sephiroth. The effect was rather strange, made Sephiroth chuckle as well and then it was hard to keep their mouths together. They made a good attempt, though.
Zack's lips didn't feel especially more arousing now that he and Sephiroth were... he wasn't sure what to call it, since exclusive was potentially non-applicable. Dating, probably.
It felt better anyway, made his throat go tight, and his chest. Zack's lips were soft, his kiss slower, more patient, it didn't promise sex in the next minute. He liked it.
He wasn't going to want to do it too often. It was distracting. The last thing they needed was a Wutaian guerilla choosing just this moment to attack; he might take a shamefully long time to notice. He broke contact slowly.
Zack drew in a slow, deep breath, and then his eyes started twinkling. "Pleasure doing business with you, sir."
Sephiroth heaved a long, fake sigh and climbed to his feet. "Get your assets back to camp, Lieutenant."
Zack snickered all the way downslope.