It was not every day Genos wished he could go back in time to forget something. In fact, he never wished for that. Except for today, as he lazily stroked his dick, a recent upgrade, while fantasizing about that weird naked man he saw merely a few days ago. It was such an unlucky chance encounter, and despite what his dick thought, he was not happy about it. He searched the internet for the man as soon as he was repaired, and found his name to be Speed O Sound Sonic, a villain. He vaguely remembered Saitama mentioning meeting a fast ninja, as he described, and wondered briefly if it was him that his sensei was talking about. He changed his pace, tugging roughly on his cock as his mind vividly imagined Sonic naked and writing underneath him. He imagined running his fingers over the man's pale body, tracing the scars that were placed there. Soon after reaching climax, he mentally slapped himself and vowed to forget the ninja and his disgusting attraction to his body. He cleaned up his mess, pulled on a shirt, and left the apartment to run.

A week passed, and Genos was frustrated. Try as he might, he just couldn't beat back his lust for Sonic. It was everywhere he went, and it repulsed him. He felt like some horny 13 year old who saw his first pair of boobs. Saitama noticed his increasing frustration, but opted not to ask him about it, sensing it was a dangerous topic, and he quite liked his apartment how it was. Small and in order, except for one pillow, which lay torn and beaten in a corner.
"I'm just going to go out for a while. Don't wait up for me, I know my way home." Saitama joked, though Genos said nothing. He just quietly fumed and glared daggers at the window. Saitama shrugged and let himself out. He hoped that upon his return, maybe by some miracle, Genos' was in a much better mood.
At least an hour passed before Genos finally moved from his position, and he went to take out the trash. When he re-entered the apartment, a warning indicator went off in his sensors. He rushed to the living room to find the window wide open, and the ninja from before was standing, in a black skin-tight suit, in the middle of the room. He was facing away from Genos, but Genos knew that he knew he was there.
"Surprised you didn't notice me coming? Am I just too fast for your sensors, cyborg?" Sonic said, smirking without turning to look at Genos. Genos couldn't believe he would let his anger and frustration get to him so much as to not notice Sonic's presence in their immediate vicinity. He would ignore the taunt, and instead clenched his fists and said nothing.
Sonic snickered.
"What? Don't you recognise me? An S-class hero such as yourself, cannot recognise an S-class villain li-"
"Speed O Sound Sonic, I know who you are."
Sonic turned to him now, the corners of his mouth turned up.
"So you do know who I am."
"If you have nothing important to say, then get out. I don't have time for you. I'm busy." Genos growled, fighting the urge to punch Sonic's stupidly nice looking face. Sonic raised an eyebrow.
"To me, it looked like you were having a staring contest with the window pane until just now." he said, crossing his arms loosely over his chest. Genos' eyes raked down Sonic's black clad body once before he managed to regain control over himself. The material was so thin, so tight, it merely did nothing except hide Sonic's scars from immediate view. A view which Genos really lik- No!
"Is Saitama here?" Sonic asked, giving the room a once over, and dragging Genos out of his thoughts. No doubt he felt Genos' hungrily inspect his figure, though he wasn't going to show it. Genos didn't respond, too angry and downright disgusted with himself to speak. Sonic turned back to him.
"Now that you know sensei isn't here, can you leave." Genos even offered him help by gesturing to the front door, though he had a feeling Sonic wasn't one for doors. Sonic yawned and stretched his arms above his head, his ribs becoming quite visible under his suit.
"I'll come back later. Besides, I can see now what you meant by 'busy'." He said, slyly sliding his gaze down Genos body to his groin. Genos followed his line of sight and looked down at himself, cursing under his breath at the tent in his pants. How he didn't notice, until now, will remain a mystery to him. It was at this point in time, he was regretting getting the upgrade.
"Just get out, Sonic."
"Or what?"
"Or you will regret it."
Sonic laughed at him. "What are you gonna do to me, huh? You can't catch me." He teased, crossing his arms once more.
In a blink, Genos had zapped forward, arms where Sonic had been. He felt a pair of slender, strong arms slide around his neck, putting him in a chock hold. They both knew the hold did nothing to stop the cyborg, but was merely Sonic showing off his speed.
"One point to me." He said, releasing Genos from the headlock and quickly hopping back. Genos turned to face him, his glare strong enough to melt glass. Sonic beckoned him forward with one finger. There was no movement for a moment. In one swift movement, almost too fast for even Sonic to see, Genos came at him. Sonic moved back, out of harm's way, certain he could avoid the cyborg easily. Unfortunately, he miscalculated exactly how close he was to the wall, and just as he tapped it, Genos was on him, slamming him against the wall. One hand held firmly around Sonic's neck, the other raised in a fist, ready to strike. Sonic's hands instinctively went up to Genos' to try and pull it away, but he knew he wouldn't be able to. The cyborg was solid and unmoving. The ninja was cornered and trapped, the two things he hated the most.
"Point to you, then. Best out of three?" a sly smirk crept across his face as he eyed Genos. Genos held him there for a moment, engaging in a stare off. Finally, without breaking eye contact, he released Sonic, and lowered his other arm to his side. Sonic broke eye contact first, glancing down in between them, then back up again so fast, Genos wasn't sure if he just imagined it or not. "Best out of three." Genos agreed, stepping back and allowing Sonic to have more moving space. Sonic stretched out his arms and cracked his neck. Then, same as before, he called Genos forward with just a simple hand gesture. This time, Genos immediately made his move, aiming to push Sonic against the wall roughly and hold him there as he grinds himself agai- NO! He hesitated as he fought off that thought, allowing the perfect opportunity for Sonic to make his move present itself, which he took graciously. Before Genos had time to react, Sonic had him pushed up against the wall he himself was stuck against mere seconds ago, and held his gleaming, new sword at Genos' throat. The ninja grinned wolfishly.
"Two points. Looks like I win." He said, pulling his sword away. The moment the sword was in its sheath, Sonic felt himself slam against the wall, face first. Genos stood behind him, holding him in place by his hair.
"You let your guard down. I win." Genos stated, tugging on Sonic's hair to prove a point. The smaller male hissed in pain.
"Heh, I'll remember that for next time." He spat, trying to turn his head under Genos' tight hold on him. He managed to twist himself enough that he could partially see the cyborg as he held him in place. "Now what? You gonna let me go, or are you gonna use me as your personal sex toy?"
Genos spluttered, his grip on Sonic loosening slightly. "W-what the fuck? Why would you even say something like that?" He said, his voice slowly growing more louder than he intended. Sonic just grinned at him and lowered his gaze. "Well, if your boner is anything to go by, I'd say you're enjoying this kinky shit." "W-what!?" Genos spluttered again, looking down at himself.
Repeating his earlier actions, he cursed himself for, once again, not noticing how tight his pants were over his increasingly large boner. His felt heat creep over his synthetic cheeks, and assumed that he was blushing. Sonic also noticed his cheeks and his grin grew wider.
"Ha! I was right! You are getting off on this! I didn't even know cyborgs had dicks but here we are!"
"Shut up!" Genos shouted, tugging on Sonic's hair again. The ninja made a strange moaning sound, like he was in pain, but with an added… something more.
"What the fuck was that?" Genos asked him, not so much looking for an answer as to just voicing his confusion.
"Stop pulling on my hair like that!" Sonic commanded, and began trying to wriggle himself out of Genos' grip. Genos opened his mouth to say something, then paused and tightened his hold on the long black hair.
"What, like this?" He pulled on the hair again. Sonic made the same moaning sound, a little louder this time. A light pink tinge dusted Sonic's cheeks. Genos' face burned.
"Let me go, cyborg!" Sonic huffed, reaching up to try and untangle Genos' fingers from his hair. His hands were shaking lightly, Genos noted. He also noted the position Sonic was in, and how he himself was positioned, and he froze. Quite literally. His body ceased complete movement and he couldn't quite comprehend what to do next. The ninja wriggled under his grip, and somehow managed to pry some of his hair out from Genos' hand.
"Are you even listening to me?" Sonic hissed, trying so very hard to pull out of Genos' grip. As if it had a mind of its own, Genos' hand released its hold and pulled the clip from Sonics hair, allowing it to freely fall down and around his shoulders. Sonic turned and stepped away from Genos, one hand going to his hair as if unbelieving of what Genos just did. Genos himself didn't believe it, and had no reason for doing what he had just did. Sonic opened his mouth, but before he could sound his complaints, Genos tossed the hair clip in his general direction, missing him and landing a few steps behind him.
"What the fuck, cyborg?" Sonic cried as he turned to retrieve the clip. Genos looked down at his hand in utter confusion. When he looked up, Sonic was bent at the waist as he snatched the clip from the floor, but that wasn't where Genos' eyes were. In fact, his eyes were glued to the ninja's extremely sweet ass. He couldn't disagree with his mind this time, as it was a very sweet ass. He kept staring, even when Sonic stood and glanced back at him, an eyebrow raised. He clipped the hair clip to his scarf.
"Enjoying the view?" He teased, running his fingers down his ass.
"Yes." Genos whispered before he could stop himself, then slammed a hand over his mouth, his eyes widening and his face on fire. "No! Not in a thousand years!" He cried from under his hand.
Sonic's face split into a huge grin as he laughed. "I can't believe this! The Demon Cyborg, attracted to my ass!" He said in between laughs.
"I'm not attracted to your ass!" Genos shouted.
"Unless you just have some secret weapon stashed in your pants, I beg to differ." Sonic snickered, covering his mouth with his fingers to hold in the laughter. Genos looked away. Any second now, his synthetic skin was going to melt off of his face, he could feel it.
"This is all your fault!" Genos shouted, pointing at Sonic without looking directly at him. Sonic raised an eyebrow and gestured to himself.
"Me? What did I do?" He asked, his voice tinged with amusement.
"I would be fine if you just didn't appear! Twice! What kind of ninja are you if you're not invisible!?"
"Hey, don't blame your boner on me. I haven't done anything except exist."
"That's exactly it! You haven't done anything, yet here we are!"
"If I could be honest with you for just a moment here, cyborg, but I haven't got a clue what you're on about."
"I don't want you to be honest with me."
"Then what /do/ you want from me?!" Sonic cried, throwing his arms in the air in a frustrated gesture.
Genos hesitated. What exactly did he want from Sonic? His eyes wandered to the ever increasing bulge in his pants. Sonic followed his gaze, the corners of his mouth pulling into a smirk.
"If you wanted some help taking care of your 'problem', you should have just said so." He teased, placing his hands on his hips. The cyborg looked up at him, frowning something fierce.
"Fuck you." He spat, clenching his hands into fists. Sonic's smirk evolved into a grin.
"Well, since you asked so nicely, I guess I could clear my schedule for you." He said, removing his sword and gently leaning it against a wall. Genos' frown became a look of pure confusion.
"What?"
"You just said you wanted to fuck me."
"No I didn't!" He spluttered in protest. Sonic unwound the scarf from his neck, placing it next to the sword, being extra careful to stand slowly to allow Genos some more ass-staring time.
"You did, and honestly, even if you didn't, it's clearly all over your face." He replied, giving Genos a sly look. Genos' mouth dropped open. He couldn't believe this was happening. Without his noticing, Sonic stepped closer to Genos and pushed his mouth closed with his fingers.
"Hello? Did you shut down or something? God, I hope there's a manual around here so I can find out how to turn you on." He said. His fingers still rested lightly under Genos' chin. Genos blinked at Sonic, who grinned back.
"Did you like that? I think it was pretty good as far as puns go."
"It was horrible." Genos replied, his voice quiet, even to him. Sonic shrugged lightly.
"I can probably make some more that are equally as bad, unless you want to shut me up." He said, his eyes holding fast to Genos'. They stayed this way for a few seconds before Sonic opened his mouth to possibly give Genos another terrible pun. Before he could make a sound however, Genos leaned in, sealing his lips over Sonic's.
He watched as Sonic's eyes fluttered closed, and he kissed him back, gently nipping at Genos' bottom lip. Sonic slid his arms around Genos' neck, pulling his closer, as Genos shakily placed his hands on Sonic's hips. He felt Sonic's fingers curl in his hair, tugging gently as he deepened the kiss. As if by their own violation, his hands slid from Sonic's waist to his ass and squeezed gently. Sonic moaned, then pulled back, their lips making a pop sound at the separation. Genos opened his eyes and fixed Sonic with an annoyed look. Sonic said nothing, just pulled out of Genos' grip completely and, one hand holding Genos' shirt, turned and walked the both of them into the bedroom. "Soni-"
"Strip. Now." Sonic said when they had reached the room. He let Genos' shirt go, then slowly wriggled out of his body suit. How he was managing, Genos couldn't tell, but the sight was mesmerising, and Genos' temporarily forgot what he was meant to be doing. Sonic had just managed to get his top half free of the constricting clothing, when Genos latched himself onto the ninja, hands sliding down to help remove the garment while his mouth worked on leaving marks on the clean pale skin of his shoulder. Sonic sucked in a breath, his head falling back slowly as Genos bit and sucked his way up his neck, his jaw, then finally, locked lips, nipping gently at Sonic's bottom lip as he had done earlier. Together, they yanked the body suit off, tossing it somewhere in the room. Somehow, they rid Genos of his own clothes, and had fallen to the floor, Sonic straddling Genos' waist as they made out passionately.
Genos whimpered as Sonic broke off their kiss, causing Sonic's face to break out into a massive grin as he slid his way down Genos' body. Without much warning, he took Genos' dick into his mouth, right down to the base. Genos cried out, and came right then in Sonic's mouth, who swallowed the sweet oils that spilled from his dick as if he had been practicing all his life.
When Genos had come down from his high, Sonic separated himself from Genos' dick, and sent the cyborg a cheeky grin.
"That was fast. And we haven't even reached the best part." He teased, slowly stroking Genos' dick as he spoke. Genos propped himself up on his elbows, watching as Sonic stroked and pumped his dick back to full hardness. He wasn't even aware he had the energy to go a second round. Sonic chuckled at the expression on Genos' face, before placing a kiss on the tip of his dick then taking it into his mouth, slowly bobbing his head up and down. Genos groaned, fighting to not thrust into Sonic's mouth as he sucked harder, and moved his head faster, taking his full length in every time. At the same time, Sonic reached behind himself and fingered his ass, preparing himself. Genos' reached down to grab hold of Sonic's hair as the ninja moaned at his own ministrations, the vibrations doing some very delicious and unbearable things to Genos' dick.
"Ha… S-Sonic…" He croaked, feeling his end near. All too soon, Sonic pulled himself off Genos' dick. Genos' whined and gasped at the feeling of the cool air blowing on his saliva covered dick. Sonic crawled forward, placing a chaste kiss on Genos' lips as he positioned his ass over Genos' dick. Then, he pushed down hard, fast, on Genos' dick, down to the base. They both moaned, Sonic's hands clinging to Genos' shoulders. Genos' hands moving to cup Sonic's ass. They waited a moment for Sonic to adjust, then he lifted Sonic and pulled him back down again, in a slow rhythm. Sonic captured Genos' lips in a teeth-clashing kiss, and moved his hips in time with Genos.
"Ah… Faster, Genos." Sonic murmured against Genos' mouth. The cyborg complied easily, pumping his dick into Sonic faster.
"Yes! There! Good!" Sonic cried as Genos' hit his prostate. Genos nipped at Sonic's neck as he aimed for his prostate repeatedly. The sounds Sonic made after that were absolute delectable.
"Yes! Genos, God, yes! Harder!" he shouted, arching his back. Genos did as Sonic instructed, his thrusts becoming harder and faster, hitting that same spot every time. Sonic's moans grew louder with ever thrust, it was a miracle Genos didn't orgasm just from the sounds alone.
"Genos…!" was all the warning he got before Sonic reached climax, his cum splattering over their chests. Genos came immediately after, crying Sonic's name as his ass clenched around Genos' dick, causing him to see stars while his cum filled Sonic's ass. When they had both come down from their highs, Sonic lifted himself from Genos' spent dick, drawing in a breath as he became empty once more. He made to leave, but Genos pulled him back, holding him close to his side, one hand immediately going up to tangle in the ninjas long, silky smooth hair. Sonic opened his mouth to protest, but Genos shushed him with a gentle kiss.
"No talking." He whispered, before closing his eyes and promptly falling asleep. Sonic sighed and ran a hand through the cyborgs hair, twirling it between his fingers.
"I didn't regret it." He whispered to the sleeping Genos. Then, he too fell asleep.

Saitama curled up on the cold floor of an abandoned apartment somewhere in Z-City. He shivered and sneezed. "Damn, I wish I remembered to grab a blanket before I left." He huffed to himself, as he curled himself into a tighter ball. "Genos better not have messed up my apartment too badly. It's not cheap to fix."