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Saitama carded his hand up Genos' neck with barely any pressure, and slid up to cup his head, thumb brushing over a pierced earlobe. Genos' shoulders slumped unexpectedly, a small thrum starting in his chest as his chin lifted, nuzzling into Saitama's fingers.
"Genos?" Saitama asked, his voice unexpectedly throaty, and Genos shivered as Saitama drew his hand back down it's path, caressing the struts that made up his collarbone.
"Sorry, Sensei," Genos said, but he certainly didn't look sorry when he swallowed and sighed, Adam's apple bobbing under Saitama's fingers.
"Does this feel good?" Saitama asked, and when Genos didn't reply straight away, he leaned down to put his lips to his ear and purred, "Genos, I asked you if it felt good when I touched your neck."
Genos gasped, his body tensing under Saitama's. When Saitama leaned back to look at him there was only a thin shine of gold in his eyes and his teeth were sunk into his lip. After a moment, he took a steadying breath and said,
"My body only possesses four erogenous zones, and you are touching two of them."
Saitama smirked down at him, and he moved his hand up to grip Genos' chin firmly, pushing it up a bit as he leaned down to brush his lips where there would be a pulse, if Genos were all flesh and blood. A muted sound kicked up out of his chest, and Genos' fingers tangled with the sleeve of Saitama's sweatshirt.
"So all this time, I could have been getting you off with love bites? Why didn't you tell me sooner?" Saitama mumbled against the soft silicone of black synthetic skin. Something thrummed buzzily under his mouth, leaving tingles behind, and Genos' body tightened again, this time in a wave that pushed his chest up into Saitama's. His body was hard, of course, but there were little tracts of that black skin that gave under his hands so nicely. Saitama's favorite was the silken little strip at either side of Genos' waist. It curved so delicately to a narrow little handhold that his free hand found, and Genos tensed again, nearly a roll.
"I didn't- I don't know if it goes that far-" Genos said, and there was a tiny bite of static at the end of his words that always manifested when he was distracted enough that he didn't sharpen his words. When Saitama opened his mouth to press a wet kiss to Genos' neck, there was another muted noise, lower and longer, and when he looked up Genos had his eyes squeezed shut, lips pressed firmly together.
"Genos," Saitama murmured, and cupped his jaw again, "Genos, is this okay?"
Genos turned his face further into Saitama's hand instead of replying, and he blinked slowly for a moment, then kissed the side of Saitama's palm. His lips were the same buzzing softness as his neck, and Saitama shifted his weight up so he loomed over Genos. He settled his hand high on Genos' throat, cupping the line of his airway, and Genos withered into the touch with a soft, open moan that sent an answering shiver up Saitama's spine.
When he leaned down to kiss his apprentice, Genos went pliant expect to arch into Saitama's hands. His mouth, warmer and drier than a normal human's, opened eagerly for Saitama. He kissed back lazily for long moments, shifting restlessly with each new breath. As soon as Saitama slipped him some tongue, his hands flew to Saitama's back and gripped at him hard, and another groan spooled out of his chest. Heat flared along Saitama's spine, disorienting at first but soon ignored. Genos was the only one who could get him aroused in any way, but he was used to ignoring the feeling by now.
Now, especially, he wanted to ignore it in favor of turning Genos on, but he hoped the cyborg could achieve orgasm. Otherwise, he knew the younger man would become frustrated with himself and retreat from affection for a few hours, by which time he would have already sent diagnostic and analytical reports to Dr. Kuseno with notes on what he hoped could be added.
Saitama knew the doctor wouldn’t have given Genos only four erogenous zones if he could have given him the same as anyone else, so it was reasonable to assume it wasn't possible.
Which meant he would try his damndest to get Genos off like this, because by now their giving and receiving ratio in accordance to orgasms was tipped hideously in his favor.
He sucked Genos' bottom lip, and with a groan that shook up from his core the cyborg had to tear away to pant, shuddering. By now his combustion engines had gone hot, and heat glowed out of the the vents out of his chest in little waves that hit Saitama in the face. It was usually nice to get all warm next to Genos at night, but now he was already warm and wearing a sweatshirt. Nervous but determined not to sweat too much, Saitama sat up and yanked his sweatshirt up over his head. The sweatshirt inverted and got stuck around his head, and he was aware that Genos was probably taking this as some sort of smooth move, since his shirt was stuck to the inside of his sweatshirt and he was bent as if he were trying to show off his chest. There was a careful touch to his hip, and he huffed, wriggling to get free.
Genos seemed to get it then and reached up to help him out. When Saitama popped free, face heated with embarrassment, Genos only grinned, a suddenly rakish and charming thing that Saitama had never seen on his solemn face before.
"It's alright, Sensei," he said, and draped himself in Saitama's arms. Saitama tugged his body flush to his own and laid him down again. For a moment they only stared at each other awkwardly, and then Saitama grinned and slid down his body to touch the warm, smooth expanse of his inner thighs with his fingertips. Genos shivered and with a touch of wary shyness, spread his legs so that Saitama could settle in between them. He leaned up to kiss Genos again just for the heck of it, and then Saitama hummed to himself as he pressed kisses onto soft, synthetic flesh. The higher he went, he found, the more Genos twitched and mewled, and when Saitama dug his teeth in to the muscle, a jolt tore up his leg that jerked his spine into an arch. Genos hissed, his hand suddenly pushing hard at the back of Saitama's head, and he took that as incentive to pepper the skin with careful bites and hard, sucking kisses. Genos shook, the heat pouring off of him making Saitama sweat, but when he reached up to grip the sides of Genos' waist as well, the cyborg was suddenly wailing at a strange and inhuman pitch, and had to flail a hand up to his mouth to cover up the sound.
Still gnawing on the strange silicone flavor of muscled thighs, Saitama reached up and plucked his hand away, letting the keens fall out of Genos' mouth. It was undeniably hot, and not just because steam was beading on his skin. Besides, there was no one within a mile to hear anything they wanted to do.
Saitama put his hands back to Genos' waist, massaging the muscle there too, feeling it flex and bow under his hands. When he dug his fingernails in lightly, Genos made a deep wounded sound and suddenly went slack. He pulled his mouth up off of Genos' thigh with a pop, looking up to ask what was wrong.
From the way Genos' body was heaving with every breath, he was close to overheating. He looked wrecked, and his gold eyes tracked Saitama with wide-eyed fervor.
"Please," he whined, barely audible through the sudden feedback in his voice, "Saitama."
That was all Saitama could take, then. He jerked his pants open, letting his neglected hard-on get some much needed air. He slid back up Genos' body, and with one hand still on his waist, he pushed at Genos' legs until they were pressed tight together and slung up onto Saitama's shoulders.
When he pressed his cock between the tunnel of his thighs, Genos threw his head back and attempted to swear, but Saitama couldn't really understand what he said. Instead he braced one hand on Genos' waist, one on his throat, and fucked Genos' thighs with a rhythm that was hard and slow. The slide was torturous, just barely slick enough, the friction from the silicone making it hot and stinging. Genos went slack again, little warbled noises of distortion eeking out of his throat, and then he was shaking so hard he clattered, pulsing his hips against Saitama's with every last bit of coordination he had.
Saitama came at the blissed out look on Genos' face, and when he could see and think clearly again, he opened his eyes and found that Genos' eyes had gone blank, and he was as limp as a rag doll.
Heart spiking with anxiety, Saitama sat back when Genos suddenly gasped and jerked, blinking several times.
"Oh," he said, "that was..." and he just grinned, a little muzzily and disbelieving, and Saitama laughed a little hysterically.
"God, you scared me there. Are you alright?"
Genos was silent for a moment, clearly running a systems check.
"I am running at maximum proficiency. In fact, I am 1.73% more proficient than I was before we had sex," he says, and Sai raises an eyebrow at him.
"So you're saying sex is good for you?"
Genos nodded, that rakish smile on his face again, and Saitama nodded back sagely. With his hair messed up and still blowing steam like a train, not to mention the come smeared on his thighs and stomach, Genos looked positively filthy.
"Well then," Saitama said seriously, "As your sensei, it's my duty to make sure you're always running at your best," he said, and leaned down to kiss his cyborg.