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Shinichi resisted being led into the changing rooms for the hot springs, but since Kogoro was off drinking again, despite Shinichi's best efforts, Ran dragged him into the women's changing rooms with her, and then into the women's hot springs. Sonoko, along with some other women he didn't know, laughed at how cute Conan was, trying to cover both his eyes and his dick with his too-small hands.
Shinichi could feel his face burning with mortification. Just because the women didn't know he was old enough to be a perv, they thought it was cute. But despite his small size, his nervous system had never been affected by the change, and his hormones raged as strongly as ever, but perhaps more densely, so the mere idea of naked women often sent blood rushing to his groin.
When everyone was naked for the hot springs, Shinichi very carefully watched his own feet and tried to ignore the bare skin in his peripheral vision. He followed Ran by her grip on his wrist all the way into the water.
Shinichi wasn't sure if it was better or worse that the other women were in the changing room on their way out, so he and Ran and Sonoko were the only people in the women's hot spring. A masculine rumble of voices was barely distinguishable through one wall, but Shinichi couldn't make out any words. Somehow, that was the detail that made him feel isolated in this hot spring with his two childhood friends. The three of them were alone together, and nude, and it felt strangely intimate.
Shinichi knew he was tomato-red, and he tried to think of the least sexy thing possible: the various murder cases he'd seen.
But with nudity on the brain, the case that came easily to mind was a model who had been murdered by her latest boyfriend during an argument, but then her dead body was staged half naked and half in sheer lingerie in an attempt to frame one of her exes. (The murderer's story had been that a masked man had broken in to his apartment while they were just about to get in bed together. But he'd been lazy about mimicking the horny slickness his ego demanded her vagina be be producing for him, and had poured lube with a distinct cherry scent onto her corpse and panties, then put the bottle back into the bedside table and claimed they hadn't had time to get anything out. Once caught in the lie, there had also been other evidence, like the brightly colored fibers under his fingernails from the lingerie he'd clumsily dressed her in.)
Kogoro was still the only adult who even put forth a token effort at keeping Conan away from murder scenes anymore, even one like this, and the man had been so distracted making heart eyes at all the risque photos of the model on the walls, that Shinichi hadn't even had to be all that careful to dodge Kogoro's attention...
Shinichi startled as Ran grabbed him in a hug and tugged him into her bare lap, where her pubic hair tickled his too-small bum. He'd been trying to block everything out with memories that were not not-erotic enough, but now he abruptly realized that Sonoko was nowhere to be seen.
Shinichi had flailed, instinctively trying to keep his balance, when Ran had grabbed him, so his hands were still spread wide, crucially, not hiding his dick, when it swelled and throbbed at the sudden, horny realization that he and Ran were alone together, and naked, in a relatively soundproofed room.
Before Shinichi could hastily cover himself again, Ran's hand was cupping him right there while her other arm was still under his arm and across his torso, holding him firmly in place.
"You're just like him," she murmured in his ear. Her warm breath and the occasional flicker of her tongue against the soft skin of his ear wasn't doing anything to help him deactivate his dick, not to mention the rest of where she was touching him.
"Ran...n-n-neechan!" Shinichi managed to gasp out. The suffix was harder than ever to remember, in such an intimate moment, and his protests dissolved before he could properly put them to words. But he knew he objected: he shouldn't let her touch him like this. It should all remain fantasies - involving him in his proper body - until he could safely return to it, at least
"You're just like your cousin Shinichi," Ran repeated, as her thumb slowly slid up from the base of his dick to the tip. Her thumb circled the head of his dick almost too roughly. But the pleasure that coursed through him at her touch was overwhelming, so much that he could barely focus on her words. "So smart, but so shy and innocent... I waited too long to demand that he share that innocence with me... but you'll also do anything to please your neechan, won't you? Just like your cousin would do anything for me?"
When her thumb slid down his dick again, his foreskin was loose enough to retract with it, revealing the sensitive head of his dick under the warm water.
Shinichi had learned to fight back against attackers who outmassed him far more than Ran did, but those tactics were for people he was willing to hurt, and while fully clothed, with the gadgets Agasa had made him. Naked, in the arms of a karate champion he would gladly have died for, Shinichi had no choice but to relent.
"Okay... Ran."
"I knew you'd be a good boy for me," Ran whispered into his ear. "Even better than your cousin."
Some part of Shinichi knew that he should be offended on his own behalf, as well as Conan's, but mostly he was distracted by her touch, and the way that someone else touching his dick sent so much more of a spark through him than masturbating ever had. He made a vaguely affirming noise as she turned him bodily around and leaned down to kiss him, right on the lips.
Shinichi kissed Ran back, despite the distantly screaming part of his brain. The warmth of her chapped lips on his too-small ones was only slightly better than his fantasies.
Ran's tongue teased along his lips, but when he gasped in a needy breath, conveniently parting his lips to let her in, she pulled back and sat upright again. Then she spun them both around, manhandling him until his narrow ass was sitting on the shallow seat she'd just vacated. She kept one hand on his dick while the other guided him to lean back until his shoulders were against a rocky wall, and the hair at the very bottom of his neck was just touching the warm spring water.
"Conan is going to keep being a good boy for me: by sitting here and letting me touch you." Ran whispered, and stepped forward to straddle him.
Shinichi valiantly resisted suckling her breasts, even when they pressed warmly into his face, and while she slowly crouched down, one hand in his lap, gently guiding his too small (yet also too big: why was his body betraying him like this?) erect cock into herself.
Shinichi was half-relieved that his grade school sized body was so much smaller than he ought to be. Her vagina, while warm and soft, was much looser around his dick than his own hand, when he chose to use it, so he wasn't likely to embarrass himself even worse by cumming inside her.
"Kiss them," she instructed, once he was fully sheathed inside her, and she tugged one of her boobs into place so that a nipple was brushing against his lips.
Swallowing his guilt and shame (and still ignoring that distant feeling of betrayal), Shinichi obeyed. He gently sucked her nipple into his mouth and licked it.
Ran made a noise that made his dick throb again, and started rocking her hips against his. The motion bounced his tiny cock against all her walls in turn and made him second guess his conclusion that he could resist embarrassing himself. This all felt alarmingly good.
Soon, Ran thrust a little too energetically, and his dick slipped free, but she continued grinding her hips against his, chasing her own pleasure.
She was clearly trying to be quiet, but her face was still so close to Shinichi's that he could hear every muffled moan and gasp of pleasure.
Ran didn't seem to notice when Shinichi came below her, teased over the edge by the occasional brush of her labia over his stiff dick.
As soon as the wave of endorphins passed, Shinichi was promptly overcome with an even stronger wave of disgust and self loathing. How had he let himself enjoy that? He'd let Ran touch him, an apparent child, under what were essentially false pretenses.
But he couldn't escape either. She was still pinning him down, grinding against him, her gasps and moans sickly sweet in his ear. Time passed by as interminably in his misery as it had in his pleasure, until eventually Ran's arms and legs all tightened convulsively around his tiny frame as she mumbled "Shinichi! Yes, Shinichi! Please!"
Even after Ran released him from that crushing hug, she didn't seem satisfied, and she didn't let him up. Instead she knelt, with her knees on either side of his hips, and her dripping bush in his face. Shinichi couldn't hide from her nudity if he wanted to.
Ran pressed her hips forward until her hair was tickling his nose and lips. "Kiss me," she instructed, and Shinichi still had no option but to obey. He kept kissing her until her instructions changed from "lower! C'mon, a little more..." with corresponding shifts of her hips, to "Yes there! Right there! More!" When that happened, Shinichi observed an unfamiliar flesh structure under his lips. He couldn't identify it with lips alone, but Ran didn't protest when he started trying to map the structure with his tongue instead. In fact, she made a happy noise, and tried to press herself even closer to his face.
Shinichi had just enough time to conclude that the nub was at the very top of the slit between her labia (labias? The lips of her labia?) and had a hood of its own, almost like an eyelid, or a foreskin, when her thighs tightened dangerously around his head.
Shinichi froze in fear and forgot to even keep kissing the nub. He could focus on nothing but the danger until Ran finally relaxed. Her powerful thighs released his head and she rolled sideways off of him, collapsing limply back into the hot springs like a puppet with its strings cut.
Shinichi blinked back the hot prick of tears behind his eyes, and tried not to be too obvious about gasping for air after his sudden release.
Then he had to try not to tense too obviously when her arm landed heavily on his shoulders.
"I knew you'd be a good boy for me," Ran whispered, around her own deep, panting breaths. "And I think you had a good time too. If you keep this our little secret, we can do it again sometime, okay Conan-kun? But if you do tell anyone they won't believe you and you'll get in big trouble for lying. Understand?"
"Y-yes, Ran-neechan," Shinichi stuttered out as sincerely as he could manage. He probably did want it again, right? It was something straight out of his fantasies. The tears he was choking back must be tears of happiness, right?
... right?