"Look at you baby, all sloppy and desperate, ready to be bred." Shiro coos, walking slowly around him, inspecting him. Keith can't speak, can barely moan around the vine stuffed down his throat, when the ones in his ass find his prostate again. Such a contrast they make. The one in his mouth is big, huge, forcing his jaw to accommodate its girth. It abuses his throat, dry if it weren't coated in his spit. When it's done with him he knows his voice will give away exactly what it used him for, but the ones in his ass are tiny, barely thicker than a pencil. They fight and squirm around each other for space in his hole. Squelching lewdly through the goo they ooze. Something in the goo forces his muscles to relax and heightens the feeling of every touch.
It makes it all the worse when they decide to continually play with his prostate. Milking him with sparks of pleasure until a steady pace of pre-cum is dripping off his cock, but they offer no relief to their tease. The thing Shiro gave him to doesn't care if he comes, "You're so good at this. Whatever I can think up, you spread your legs and take," Shiro says, brushing some of Keith's sweat matted hair off his forehead. Keith tries to whimper, tries to beg with his eyes for Shiro to give him the release that the thing denies him, "It's one of the things I love about you, how eager to please you are." As he talks, Shiro's cool metal thumb traces along Keith's stretched lips. The bits of softness are almost enough to distract from the pleasure building unendingly in his gut and the rawness of his throat, "I think it's ready for you. You're going to be such a beautiful incubator." Shiro's smiling, looking at something behind him that Keith can't see.
The words incubator, make him uneasy. He thought the general was being metaphorical in talking about breeding him. Just wanting to fill him up with some alien's cum like normal. Now, he doesn't know what he's about to be used for.
The small vines inside him rearrange, some slipping out, more pressing against his rim. Holding him gaping and open, waiting. He can't squirm away when the new vine pushes against his hole, can't close himself up to keep it out. All he can do is sit back and feel the way the massive thing breaches his hole. It's width forces out the smaller vine, through size alone. The skin of it is textured. Not enough to truly catch, but enough to send little shocks of recognition from his rim at the lack of smoothness. It presses deeper and deeper, until it feel so far inside him that he swears it should be pressing against his heart before it stops. Keith wants to look down. Wants to see the thing that the night has built up to, but he can't. He's spit roasted between the two vines. On display, but unable to move.
That's when he feels the first expansion. The vine doesn't move, but something inside it does. Sliding along, forcing his rim wider and wider to accommodate it. The little vines stretched him well, but this thing feels like he's being forced to accept Shiro's closed fist. His heightened sensitivity lets him know exactly how much his ass stings in protest. Pain growing sharper until he thinks he's going to split open, then suddenly the thickest part is past. Keith's rim contracts, and he pants in relief as the thing travels deeper inside him, "That's one," Shiro, Keith had almost forgotten about Shiro, so focused on the thing inside him, "Let's see how many more you can take. I bet you will surprise us both." Keith's eyes widen as he feel the vine pull out just slightly and something else begins to force him open.
Keith takes five giant egg shaped things before the plant lets him go. Releasing him into Shiro's waiting arms. He can feel every single one inside him. Taking up space and making themselves known every time his abdomen so much as twitches. One has been planted against his prostate, continue the stimulation its mother started. Keith buries his head in Shiro's shoulders with a whine. The things inside him scare him a bit. He can imagine them hatching in there, tearing at his inside, then writhing out of him in some sort of fucked up birth. He needs them out before then.
Shiro lays him down on the bed, reaching for a wet cloth to clean up between his thighs, "Shiro," Keith croaks, his voice ruined, "Get them out," Keith begs, grabbing onto Shiro's wrist.
Shiro tilts his head in puzzlement, "But why? Knowing you're stuffed full and incubating them is half the fun." Shiro's finger press down against his belly, as if he can feel the eggs inside Keith.
"I don't want them to hatch," Shiro must hear the fear in his voice, because suddenly he's being wrapped up in warm arms and tucked under Shiro's chin.
"Oh sweetheart, they can't hatch. I had the creature sterilized before I let it anywhere near you," Shiro presses a kiss to his hair, "Letting something like that happen inside you is dangerous. You could be hurt or die. I'd never risk you for a little play." Keith feels himself relax. He should have trusted Shiro more. The general loves him, he should remember that he'd never endanger his life for these sessions.
"How about this?" Shiro hugs him a little tighter, "Let's get you off, then we can cuddle until your muscles work again. Then you can push these out for me, while I hold you. If you're up to it, I'll fuck your sloppy hole just like you like it afterward. That sound good?" Keith shivers. That sounds more than good. He nods against Shiro's chest. He's looking forward to it.
Figure it should be mentioned here. Keith and Shiro's relationship may be consensual, but it is very much not safe or sane. They didn't negotiate kinks ahead of time, and Keith doesn't always get the most detailed explanations on what he's agreeing to. They don't have safe words, but they also don't do roleplay, so assuming Keith's mouth isn't full Shiro has and will continue to stop if Keith asks him too.