Genos doesn't exactly have a cock. He does have a dildo like extension that he had requested Dr Kuseno to attach for Saitama's use. Saitama hadn't met Dr Kuseno before, but if he did, he would thank the man profusely for being such a genius. Genos also had an opening for when he removed waste from the food he ate that could not be converted to fuel. Dr Kuseno tried to mimic the actual human body, and placed a small sensitive surface within that acted like the prostate. It was one of those days when Saitama and Genos decided to experiment further with Dr Kuseno's brilliant inventions.

Saitama was carefully maneuvering his fingers around that opening, brushing across that surface only to watch Genos jerk and arch his back in pleasure. He had three fingers twisting in and out, slick with the oil that Dr Kuseno had given them. Apparently it enhanced Genos' senses, triggering more stimulations to run up and down his body.

"Sen.. Sensei," Genos moaned out. Saitama twisted his fingers to jab at that spot again, and he could see actual steam coming out from Genos' back. The sound of the machinery inside Genos whirred even louder as Genos twisted from side to side. Genos ran so hot that he had to release the steam from his machines whenever they fucked. Saitama couldn't help but find that fucking hot.

Saitama removed his fingers and Genos lifted his head up to look at him in alarm. Saitama merely placed a hand on Genos' chest before reaching out and claiming those lips. He kissed him hard, biting Genos' lips, and sucking on them. It was so wet and dirty, causing Saitama's own cock to spurt out precum.

"I'm going to ruin you," Saitama whispered. "Will you be good for me Genos?"

"Yes sensei," Genos cried out. As if he could do anything with his hands bound tight with the chain that Saitama had bought. Saitama spread his knees wide and finally showed Genos what he had recently obtained.

"Is that- ?" Genos breathed out slowly, his eyes wide, as if he could not believe his luck.

"Yes," Saitama smirked. "Is this okay?" he asked then, before placing the dildo that could provide electrostimulation into Genos' opening.

"Yes, please, fuck!" Genos moaned as Saitama eased the already lubed up dildo up the opening. He slowly pushed it in, and he could see Genos trembling. He laid one hand on Genos' thigh, "You're doing so well Genos," Saitama murmured as he bent and lick a strip up Genos' dick. Dr Kuseno was a genius, Saitama decided when Genos moaned, and his dick strained even further. It may have been made from silicone, but it was just as sensitive with each lick causing Genos' cock to jerk and release a whitish substance mimicking semen.

He pushed the dildo up and down, pushing against that spot that got Genos keening and thrashing. "More sensei, please, ple-please!"

Saitama breathed heavily, fire running through his veins. He wanted so badly to grab his cock and jerk off, but this was about Genos and he wasn't about to forget that.

He turned the setting to the lowest number on the dial, and watched in fascination as Genos jerked once, arching his bed, and screamed soundlessly. The stimulation was supposed to run through Genos' entire body, catching him with pleasure everywhere. If this was how Genos felt at the lowest setting, Saitama couldn't wait to bring it up till 10.

"Genos," Saitama murmured as he laid on top of Genos, one hand pressing the dildo deep within. Genos lifted his head and caught Saitama in a searing kiss. Saitama took the opportunity to turn up the dial further and turned it on again. Genos' breath was punched out of him and he moaned into Saitama's mouth.

"Sensei, I can't.. Sensei, let me.." Genos started to babble. His wrists were bound tight but Saitama could see that Genos was going to break the chains that bound him soon.

"Be good for me Genos," Saitama said, his voice cracking and rough with desire. He wanted nothing more than to pound into Genos, just making him scream for Saitama.

He slid down, his hand firm on Genos' thigh as he dragged the dildo up and down again, making Genos beg.

"You look so pretty like that Genos," Saitama crooned, "All tied up for your sensei. If only you had skin, I'll bite every inch of it, making you bleed for me Genos."

"I'll do anything.. Sensei.. Sensei!" Genos screamed as Saitama turned on the electrostimulation again. His cock jerked and Genos came, white liquid splashing all over his torso.

"Genos, you came without my permission," Saitama growled.

"I'm sorry, I'm sorry sensei!" Genos could easily get hard again, his system allowing multiple orgasms to wreck through him. They were stimulations overloading his system, causing him to experience a rush that was like having an orgasm. Saitama had found out that Genos had a very short refractory period as well, and that came in handy many times.

"For that Genos, we're going to play a little longer," Saitama murmured as he stroked Genos' dick up and down, getting it firm again. It hardened all the way when Saitama tongued at the slit, the taste much like a rubber dildo, with the faint essence of vanilla from the white liquid. What kind of crazy scientist mixed vanilla with something that was supposed to resemble semen? One who was a genius.

Saitama sucked on Genos' dick, chasing the taste as it dripped downwards. He let his saliva run over the hot cock, before slurping the whole thing down. Genos jerked and swore, and Saitama knew that Genos had broken through the lock already when Genos' hands came to grip Saitama's head. It was a pity he didn't have any hair for Genos to pull. He bobbed his head up and down, sucking on it hard.

Saitama glanced up towards Genos and quirked an eyebrow before turning that machine on the whole way through. Genos' body jerked, and he could almost see the currents running through Genos' entire body, making it pulsate with pleasure. Genos screamed as his cock pulsed and shot out that vanilla tasting liquid down Saitama's throat. Genos fell back, his hands falling to his side. Saitama would have thought he killed Genos with the sex if it weren't for the whirring sounds from Genos.

Saitama removed the dildo, and jerked off roughly to the sight of Genos slumped down, chest heaving, and face bright red. Steam was coming out again from his back, and Genos glowed.

"Fuck, you look so good Genos," Saitama said, his hands tugging onto his cock with sharp movements. He came almost too quick, from the sight of Genos so ravished spurting all over Genos' torso.

Saitama slumped down then, ignoring the sticky feel of the slowly drying cum. He reached out and dragged Genos for a kiss, a slow kiss that quickly turned hot and heavy, sending heat down Saitama's gut.

"Thank you sensei," Genos said shyly as he broke the kiss, his hands reaching around to hold Saitama close. "Can we go again?" The cyborg said, and Saitama smiled.

He had his very own insatiable sex cyborg.

"Why don't you fuck me this time instead?" Saitama murmured, and that was definitely Genos' cock twitching, taking an interest.

Yeah, Saitama was going to die from too much sex.

But what a way to go.