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Sometime after Luffy turns eleven, his scent starts to change. Ace knows that that’s when boys start to grow, not just bigger and taller, but hairier and rougher and stinkier. Luffy’s still his tiny little baby brother, but one aspect of him definitely grows and grows until it’s unavoidable and Ace feels like he’s going crazy because only he seems to be affected by this massive change, as if no one is seeing (more accurately, smelling) how pungent Luffy is becoming. It must be due to his half-mink nature, the dog side of his body dominating his human sensibilities.
He makes this realization while they’re wrestling. Ace already forgot how they got to this point; so much of what they do ends in blows. Maybe they were fighting over food, fighting over who had the bigger kill, fighting just for the sake of fighting. But when Ace plummets head first into Luffy’s lap when he tackles his brother to the ground, the revelation he makes there is the only thing that matters.
There’s something between Luffy’s legs, completely foreign. For a second he thinks that Luffy might be holding some food in his pockets, which he tends to do, but the scent doesn’t resemble anything he’s eaten before. It’s meaty, but it’s not meat.
It’s mouth-watering.
He inhales too much of it all at once and comes up gasping at air like a fish out of water. Luffy lets him take a breather before he resumes wrestling with Ace, still maintaining his sense of honor not to strike when his opponent is down.
“Wait!”
Ace grabs his hips, somewhere he rarely touches so Luffy knows he’s serious. Luffy blinks out of play-mode.
Ace leans forward and starts smelling Luffy’s body. He circles his head and his neck, under his ears where he knows Luffy sweats the most. The smell there is odd, but muted–the beginnings of something new.
“What are you doing?” Luffy asks. Ace’s nostrils flutter as they travel down Luffy’s stomach. He wants nothing more than to break past the filter of Luffy’s shirt so he can do a closer inspection with his nose.
“Need to check you. You reek and it’s weird.”
Luffy preens under the attention of Ace’s sniffing. It’s not often that Ace lets himself cave to the needs of his doggy half, but Luffy always relishes in the small slivers of his escaped nature, biting back a smile when Ace goes sniff-sniff-sniff around his knitted knees. Ace frowns, and he contemplates biting down hard on Luffy’s flesh, but it would only prove Luffy right about his undeniable biology.
Luffy squeals a short burst of laughter when Ace prods him with his nose under his thigh, where his skin is ticklish. But he’s not so peppy when Ace’s snout slides up his leg.
“No, Ace! Don’t go close to there! That’s my private area!”
“Huh? Why not? We’re brothers.”
Luffy frowns. “Dadan said no…”
His hand cups over his crotch. The display of his stubby fingers are stark against the blue of his shorts, emphasizing his petite size. It’s a weak, flimsy barricade that Ace immediately brushes aside with his nose like a doggy door, and he gets back to exploring this strange smell.
“Stop!”
Luffy scrambles up and away on his hands and knees, scooting across the grass, but Ace follows him, biologically privileged with age and strength and size and the innate ability to walk on all fours, chasing Luffy’s butt with his sniffer.
His snout digs into Luffy’s buttcrack. Luffy squeaks, shivering from head to toe that vibrates through Ace’s body too. Ace thrusts his nose in deeper, testing the fabric there, and there’s this thing underneath Luffy’s shorts that give way, unlike the rubbery bounciness of Luffy’s skin.
His eyes go wide as his senses are flooded with a wave of funk. That’s where the odor is from.
“Luffy, take your pants off. I think there’s something underneath,” Ace says. His voice is low. He doesn’t sound like himself, still young and small. He feels like an adult.
“Uh, yeah! That’s just my no-no spot! I don’t want you to look at it!”
“There might be something happening to your body! Please,” Ace begs. He needs to get at it. Just a little taste will be enough. “Please,” Ace croaks again. “Trust me.”
He can’t see Luffy’s face from here. Only a gentle shivering, but his pause speaks volumes. Ace’s maw opens up, almost delicately, and his fangs hook around the waistband of Luffy’s shorts, just scraping over his skin. He struggles with tugging the shorts over the fattest part of Luffy’s body, but with enough effort and a small rip in the waistband, the shorts come down around his thighs. Luffy’s ass pokes out of the waistband, much like the sun setting on the horizon of the sea.
Ace rarely gets to see Luffy from this angle. There’s not much opportunity to do so, even with all their rough-housing. He’s not even sure what this thing is, besides being the place Luffy pees from. Since he’s known Luffy, Ace had been aware that their parts were different but he never knew why.
It’s similar to the lips on Luffy’s mouth, the same color, the same wrinkled skin. He sniffs it curiously. It twitches like it has a mind of its own, contracting and releasing. In a way, it seems to invite him.
“Let me… lemme lick you, Luffy. I’ll lick it clean,” Ace whispers.
Luffy mumbles, but even with Ace’s enhanced hearing, he can’t really make out what he said. Maybe it was just nonsense, and Ace chooses to ignore it before he laps once against those lips.
It feels distinctly wrong, like Ace skipped a step in the process. Ace won’t lie. He’s wanted to kiss Luffy for a long time, but he’s been too chicken to ever make the first move. Now he’s laving on those folds down there, his first kiss with Luffy on the wrong lips.
It tastes how it smells. Vivid, powerful. Rich. There’s an acrid aftertaste of piss, but it’s so miniscule that Ace licks through it.
There has to be more on the inside. Ace knows that the stench is coming from in there. He needs to breach the surface.
He pries around for an opening on the surface of Luffy’s ruddy skin. Luffy cries out and tries to crawl away once again, but as always, Ace hounds him and his nose never strays from his backside. He continues feasting on Luffy’s weird sweat, his tongue like a knife on meat, trying to find the right spot to slice down on for a clean cut.
It’s at the top of those vertical folds that Ace finds a gap. He digs in, only this time he’s not kicking up dirt with his leg to find treasure. His tongue does the work for him. The taste inside is just more. Nothing like Ace has ever tasted before, nothing like food, nothing like the once-mild sweat of Luffy’s skin.
“It feels weird, Ace!”
“Just a little bit more.” Ace tries to say, but his mouth is muffled by Luffy’s lips. He groans into Luffy when Luffy’s insides squeeze his tongue and more of that burning smell and taste gets released. It’s an endless cycle of reactions, Luffy’s outpouring of juice and miasma egging Ace on and Ace’s prying tongue pulling them out from Luffy.
“Something’s coming out!” Luffy cries. His hole clenches around Ace’s tongue, and Ace has to stick his snout as far as he can against Luffy’s smelly lips, unable to breath anything but the oversaturated gas of stench that he tries so hard to lick out of Luffy like when they would both find a tree gushing with sap, tonguing their way in to eat at the tree’s treasure trove. They’d come up with splinters and ants in their mouth, but this time Ace is digging into soft, melty flesh. If only Luffy could taste himself right now, then maybe he’d understand why Ace is so fervently eating him alive.
His tongue gets suckled deep into the end of the cavern with each crushing squeeze, and it‘s got him in a chokehold. Something that smells somewhat but not entirely like pee sprays out like a geyser from the bottom of Luffy’s folds, dousing Ace’s chin. He wants to drink that up too.
When Ace manages to wrangle his tongue out of Luffy, his little brother immediately takes off like a rabbit out of the loosened maw of a wolf. Ace sighs. He’ll let Luffy have some time to himself.
He licks his chops. His tail is wagging inside his shorts, batting against its cage of fabric.
It's not the only thing straining inside his shorts. There’s something burning down there and it’s pushing at the waistband. For a second, Ace wonders if something’s crawled up his shorts. He pulls them away from his waist to check. Something flaming red and pointy springs out from the top of his hardened thingy.
Huh.