It felt like all it took was a single blink for Tanjiro to go from riled up with excitement for his new learning opportunity to blearily nuzzling into soft fabric, groaning from the ache in his neck. He felt wetness smear over his lip as he moved, propped himself up and peeled away and realized he’d been drooling into the flame pillar’s shoulder.
“Sorry, Rengoku-san,” Tanjiro mumbled, too asleep to be properly embarrassed. Rengoku was still sitting upright with his hands crossed over his stomach, so stiff that Tanjiro might not have realized he was asleep if not for his head lolling to one side. He absently reached over and smoothed the fabric over Rengoku’s shoulder, turning to squint out the window. It was still dark, but a faint ring of blue light was beginning to form on the horizon.
Tanjiro’s eyes burned. If he was being honest with himself, he just wanted to go back to sleep - but there was something tingling in his sinuses, something faint but certainly not malicious in intent. He didn’t particularly care to figure out what it was in that moment, so he turned back and placed his head on Rengoku’s shoulder before he could second-guess.
But the scent was stronger now, even with just the slightest shift in position, and Tanjiro wrinkled his nose in discontent. He groaned once again, opened his eyes, and waited for them to focus in the dull light of morning.
Dark floor, dark wooden seat, dark pants of his superior all blending together until he finally focused on the bulge at Rengoku’s groin.
Oh. He recognized that smell now.
Embarrassment peaked inside him, much more compelling than the embarrassment he’d felt about the drooling problem, and his exhausted mind struggled for a long moment. The bulge in Rengoku’s pants was big, definitely big enough to be noticed by passersby, and the sun would be rising soon, rousing more passengers. Tanjiro knew these things just happened sometimes, god knows they’d happened to him, but he’d never fallen asleep in such a public setting before. Was there a protocol for this kind of thing?
Cover it, cover it. Nobody else needed to see this. Tanjiro pulled just far enough away to remove his haori and throw it over both of their laps, blearily thinking through his options. They wouldn’t arrest him for public indecency, would they? Tanjiro didn’t even want to entertain the notion of losing his aniki so soon after meeting him. And even barring that, if Rengoku were forced to get off the train with such an embarrassing condition, would he even want to see the three of them again?
There had to be something Tanjiro could do. The haori had covered the worst of it, but there was still a bump where Rengoku’s - his - where the problem was. Tanjiro blushed to even confront the thought of its presence, then shook himself - It wasn’t like he’d never dealt with things like this before; he’d comforted Takeo when he’d had his first, very confusing erection and been too scared to approach their parents, after all. He needed to stop being such a baby about this.
He lifted the haori just to have another look at what he was dealing with. Rengoku’s fundoshi hadn’t come undone, had it? It felt like the bulge was much too prominent, much too explicitly what it was even with his pants done up for there to be anything underneath. Tanjiro felt a measure of secondhand embarrassment at the thought… He didn’t know how he’d ever face someone under his own command if they were to catch him in such a compromising situation.
So that meant… It was up to him, wasn’t it?
He could get Rengoku’s attention, but he didn’t like to think of his aniki expressing disappointment in him, or god forbid, calling him a pervert. He was still so hard to read, Tanjiro reflected, casting a look at his sleeping face.
Handsome, though. He was certainly handsome.
So, no, he didn’t feel that that was an adequate solution. But what else could he do? People would begin waking up soon and it wasn’t like he could just take his senior in hand without his consent.
… Or. Or, in the interest of his, Zenitsu’s and Inosuke’s training, in the interest of preserving Rengoku’s pride, in the interest of -
No, no, no, he couldn’t, it would be wrong. It would be a horrible breach of the burgeoning trust between the four of them, and if he were caught, he would be placing his friends’ futures in jeopardy as well as his own. He would be a criminal.
Maybe, Tanjiro thought, straightening up, scanning for other alert passengers, maybe, just maybe, it would be okay as long as he didn’t make skin-to-skin contact. It would be subtler than if he actually touched it and easier for Rengoku to hide once he woke up.
It’d be uncomfortable… But it would be easier to hold himself together, to carry on bonding with his new kouhais, if he didn’t need to worry about freaking them out. He seemed pretty hard, maybe all it’d take was a few tugs before the problem was gone.
Tanjiro sent one final look over his shoulder - yes, he was the only one awake. He leaned around Rengoku’s body to make sure Inosuke and Zenitsu were still… Was Inosuke on top of Zenitsu? Wild even in his sleep, that one.
It was now or never. Tanjiro adjusted the haori, made sure both of their laps were covered, and reached over underneath the cover and grasped for Rengoku’s erection. His fingertips brushed his thigh and jerked away, his heart already racing, eyeing Rengoku’s face to see whether he would stir. He was still, granting Tanjiro the opportunity to lean into his shoulder and go groping again; he let his hand linger on his thigh, just breathed and squeezed and felt how firm it was under his fingertips. Rengoku was strong, so strong, and it bled through in every part of him… it was thrilling to contemplate.
He mustered his courage and finally drew his hand up Rengoku’s leg, up and toward his - cock. He could feel the warmth even through the sturdy material of his pants; he was unsure if the moisture was because of his palms sweating or Rengoku’s arousal, but it made his hand stutter over folds of fabric as he wrapped his fingers around his shaft. He was certain that his superior’s undergarments were either out of order or absent altogether because he could get his hand all the way around and feel the coronal ridge as he tugged upward.
“Hm,” grunted Rengoku, loud and clear enough that Tanjiro jumped, withdrew his hand and watched him for a long moment. His head rolled around such that his chin was resting on his chest now, but he was still out cold.
His heart was pounding all the way up into his throat. Tanjiro swallowed and re-thought his strategy; over the clothes was just a bit too awkward to work, not quickly anyway, and the sun was breaking over the horizon. He needed a faster way.
Tanjiro bent forward, peeled his haori back a bit, and eyed Rengoku’s belt. Sneaking his hand through the opening in his pants would perhaps have been easier were that not present, but he was running short on time and he didn’t see a better solution. He gave Rengoku another glance, then reached forward, realized he wouldn’t be able to do it with just one hand, and slowly, slowly glided off the seat so that he could squat at eye-level with the belt.
This vantage point was… a little much, if he was being honest with himself. It brought Rengoku’s powerful, boxy shoulders front and center, not to mention his sleeping face. Tanjiro’s shaking fingers fumbled with the belt while the thumping of his heart took on a new tone; he glanced to the side again, threaded buttons through eyes while he checked to make sure his companions weren’t watching, and faced forward before taking a deep breath.
It was now or never. His fingertips tingled as he pushed them through the opening, fumbled briefly with Rengoku’s loose fundoshi, and brushed searing-hot skin.
He gasped, yanked his hand away, and clapped both of his palms over his mouth. This was affecting him more than he’d thought it would. His own cock was growing hot and he rubbed his thighs together uncertainly - what if he went to all this trouble and just got clocked for his own perversion?
He couldn’t think about that now. He swept his haori off of Rengoku’s lap and wriggled closer, pressing himself between his calves and straightening so that he could see what he was doing while he finally pulled out Rengoku’s cock.
It was - it was big. Tanjiro swallowed and bit his lip, tugged with shaking hands, sliding up over velvety foreskin and hesitating just under the rosy, shining head. He was salivating - he’d seen other people’s, you know, before, but never quite so close, never erect, and the scent -
He pressed forward like he was being pulled by invisible strings, opening his mouth without even giving it a second thought. What if - he just -
He barely tasted salt on his tongue before a leg jerked and an involuntary noise peeled out of Rengoku’s mouth. Tanjiro stiffened with his tongue half-out and his eyes on Rengoku’s face. His eyelids fluttered, but remained closed.
Tanjiro kept his gaze on him while he opened his mouth, mindful of his teeth, and sealed his lips around the head of his cock. He sucked, unsure of what else to do but utterly hypnotized by the scent clouding around him, and drew the tip of his tongue up Rengoku’s slit. He tasted salty and bitter, hardly a fit breakfast for anyone, but -
But Tanjiro wanted to sob from how good it was, how delicious it felt and smelled and tasted, caged by powerful legs and choking on musk. He pressed down deeper and moaned before he remembered how imperative it was that he remain silent, then felt his eyes grow wet; he wanted to savor this moment, to draw it out and listen and feel until he was sated, but he had to make it as quick as possible.
He pressed down again and withdrew, knowing it felt good with his hands and hoping it would have the same effect here. His teeth grazed skin and he winced, but Rengoku didn’t seem to react, so he bobbed again, then again. Rengoku’s cock twitched like a living thing, a wild animal that Tanjiro had to pacify, and despite himself Tanjiro let out a low whine.
Bitter cut through the salty taste on his tongue, and Tanjiro realized that Rengoku was likely getting close. He tried not to be disappointed, and instead he pulled off and kissed down the side of it, fighting to imprint this image, this taste, this scent in his mind forever. Rengoku was beautiful, this scene was beautiful, and it hurt to know he would likely never be granted this privilege again.
Something brushed through his hair and cupped the back of his head like it was trying to comfort him. Tanjiro hummed his appreciation, then gasped and looked up.
Warm sunlight passing through the window set Rengoku’s golden eyes alight. He pressed a finger to his lips and whispered, “Finish what you started, dear one.”
Heat flooded Tanjiro’s cheeks. He knotted both hands in the loose fabric at Rengoku’s knees and opened his mouth, wanting to apologize, to explain, but Rengoku shook his head. Tanjiro understood - they were in a compromising enough situation already, it was best to resolve things fast.
That in mind, Tanjiro turned his attention back to his task; he took Rengoku in his mouth again and pressed down, then startled when he felt Rengoku’s hand pressing him even further. He looked wide-eyed at his superior, feeling the head kiss the back of his throat and then push down, down, threatening to make him gag. His breath stuttered on its way through his nose and Rengoku winked.
Punishment was coming. Now was simply not the time.
Tanjiro winked back, and Rengoku chuckled before letting him go. He was left to continue bobbing, doing his best to cover his teeth, while Rengoku placed his elbow on the armrest next to him and covered his mouth in his attempt to look casual.
He pulled away to flick his tongue over the slit again and Rengoku tilted his head back - when Tanjiro looked up at him, his eyebrows were knit together, tented while the rest of his expression folded open. His cheeks were red and Tanjiro realized he was about to finish.
He covered the slit with his mouth just in time for Rengoku to spend himself; ribbons formed and broke on his tongue and he struggled to swallow, feeling an odd little thrum at the sheer debauchery of it all. To think he’d become an adult in such a public place…
Another moment, and Rengoku’s hand was back in his hair, stroking him as he peeled away, feeling his own saliva sticky on his lip. He rested his head on Rengoku’s knee as he tucked himself away, letting out a low hum of pure contentedness. He wondered if his aniki would ever let him do that again before fingers cupped his jaw and tilted his head upward to make eye contact.
Rengoku smiled, then jerked his head to the side. Tanjiro looked in the direction he’d indicated, only to see Zenitsu and Inosuke both sitting ramrod-straight and very purposefully not looking at him.
Tanjiro suppressed a tiny scream. He would never, never live this down.
Rengoku patted the seat next to him and Tanjiro jerkily did as he was bid. Rengoku offered him his haori and Tanjiro gratefully laid it over his lap.
“Now,” Rengoku cleared his throat, “I’m sure you realize I can’t let my tsuguko get away with a stunt like that.”
“Mhm,” Tanjiro replied, too stiff and too humiliated to react in any other way.
“So I’m afraid we will not be taking care of this,” Rengoku continued, casually reaching over to press a finger to the tip of Tanjiro’s clothed, hidden erection, “until we’ve reached home.”
Tanjiro almost couldn’t believe it. He straightened and looked Rengoku in the eyes. They were sparkling with mischief.
“Yessir!” he agreed, excitement fluttering in his chest.