Ryan sucked in a breath while he still could, the warm, sticky slickness of his own damn choice already soaking through his fur and sealing his body in against itself. All around him he felt the rhythmic thumping of the larger animal’s pulse, soft yet firm flesh throbbing against him, squeezing him up against the thick, supple walls around – and only further driving the tiny mouse’s footpaws into the sludge and grime that had gathered further down, squishing the thick, oily stuff up around himself.

At first he had thought it would be a good idea, thought and fantasy and desire warring within him, driving him forward towards the sleeping beast. A black and red Furfrou Pokémon, the actual inhabitant of the house in which Ryan had made his little home within the walls; a Furfrou with quite the set of equipment bouncing, jiggling, swaying between his hind legs, and with his chosen nap spot close enough to the hole to Ryan’s domain that often the mouse just sat there by the doorway watching. Days stretched into weeks, and before long the mouse found that his desires were fast getting the best of him – so he had ventured out while the Pokémon slept, took a few sniffs of that thick, pungent sheath, lost himself in his arousal… and then lost himself again within the thick, wet folds of overlapping skin and unwashed grime.

At first disgust and disdain thrummed through him, but then as the stuff welled up around his hips and chest, sucking in against his body so that his pelt flattened his against skin, dense oils and juicy flakes of old skin and stale piss sealing around him in another tight coating, he couldn’t help but grind and thrust into it, arousal prevailing over everything else. It reeked so, so strongly of this Furfrou, and every time Ryan pressed out against the Pokémon’s sheath with his paws the slick, greasy inner layers of skin just slid over his pads and slurped back in around him again, effectively pushing him deeper into the dog’s sheath. He either faced out against the interior walls of this cupping of wet, supple skin, or inwards against the firm heat that regularly slipped and slid against him, the Pokémon’s length dwarfing the little mouse’s entire body.

“I know you’re in there,” the Furfrou had said earlier, loud enough to shock Ryan out of his indulgent depths. He had squirmed and wriggled, resulting in the Pokémon shifting and throbbing against him, holding him in place between a steadily growing shaft and the inside of his sheath. “I’ve seen you watching me. What, little mouse? Wanna stay in there for good? Forever?”

He had hoped that the Furfrou would be able to feel his vigorous nodding at that, or maybe would take his refusal to leave as a sign. And, so far, that seemed to be the case: a short time later there was the dizzying sensation of the world swirling around him, the feeling of being bounced and jiggled and swung in the open air, and now the lips of the Furfrou’s sheath, wet and dripping with effusions and slime pressed out from deeper within at the mouse’s presence, had started to pull closer together.

Of course it was something that Ryan had noticed in his previous ogling. The Furfrou occasionally wore a piercing, or rather two of them, through the soft, supple skin at the end of his sheath, one directly above and one directly beneath where his tapered tip occasionally poked out. In place like this he could squeeze out just far enough to squirt across the floor underneath him, while the rest of his arousal remained caught within the thick, elastic skin, now with Ryan trapped against it… and the mouse looked up again as the free space allowed to him steadily worked itself smaller, and tighter, and slimmer.

Then he pushed his paws out at these inner layers again, squirmed, felt himself slip around just by how thoroughly the Furfrou’s unwashed slime had slickened him up, then drifted down into the grim until it slopped up around his waist again. His eyes watered, his snout felt like it had curled permanently against the acrid stench, and each time he felt a chunk of sludgy slime squish between his lips or melt between his teeth, his throat tightened under a reflexive gag.

But still, he loved it. He turned himself around again and wrapped his arms along the Furfrou’s semi-permanently sheathed cock, deliberately dragging his tongue through the coating of grease and gathered slickness. It pulsed in response, the entire space around him tightening again. He felt his chin dragged upwards at the natural response throughout the Pokémon’s buried shaft, trying to grow out of its sheath, unable to for the twin barbell piercings keeping the lips closed.

“Name’s Vienna,” the Furfrou went on from outside, voice muffled. “I’d ask yours, but it really doesn’t matter. Just know that you’ll be in there for, ah… well, we’ll see, right?”

Ryan swallowed again, felt another greasy lump roll down his throat and plop into the pit of his belly, then shivered and grinded up against the Furfrou’s sticky, slick cock. It pulsed against him again, his footpaws starting to lift out around Vienna’s slowly swelling knot trapped here inside.

“At least you’ll have plenty to eat while you’re in there…”

~ ~ ~

Vienna gritted his teeth and bore down there in front of the mirror, hips reflexively pumping forward and back, forward and back. This damn little mouse squirming and wriggling inside of his sheath, touching at all of his buried spots that barely ever saw the light of day – and certainly wouldn’t now – and squeezing on him in ways that made him gasp, and jerk, and shudder, and… the Furfrou tossed his head back, swallowed, and just barely managed to peek open one eye to watch himself in the mirror again.

Fat sheath swollen around his own fully hard cock, knot pushing out at the base, the indistinct lump of some strange tiny creature caught there against him, pulsing into slight clarity with each teeth-gritting burst of his orgasm as it pumped through him. The Furfrou’s tip twitched and trembled there between the barbel piercings keeping everything inside, each spurt of his load spraying out across the floor with such force that the sound made his ears flick.

Panting gently, legs shaking, sheath feeling just as full as it had before, the Pokémon swallowed again, leaned down, and lapped at the dripping lips there, thick with oozing grime and dripping cum. His own taste sent a shiver of acrid bitterness down his throat, but this too just made him throb again – and then a little pink mouse’s nose poked out between the piercings, just long enough for him to see.

Then a little flash of bright, sharp eyes, a slow blink, and a huff of lust-drunk breath. Vienna scoffed, buried shaft still pulsing and dripping down along the underside of his sheath.