This is just random scenes from the ficlet, but basically, Sasuke returns to Konoha and finds out about Naruto/Haseo. And isn't pleased. Not at all.
First couple of paragraphs:
Sasuke didn't like that bastard Haseo one fucking bit. And he trusted him with Naruto even less. Naruto was blindly in love with that boy from another world, and Sasuke suspected he wouldn't even fight back if Haseo suddenly decided to slit his throat one day.
It was a good thing Uchiha Sasuke was back, because now he could make sure that never happened. Naruto could thank him later.
Later on:
Sasuke woke, noticing before everything else that his body was sore, and that his lips felt like they had been bitten raw. Which they had been. By Haseo.
Memories came flooding back of the previous night and the amount of alcohol involved. Sasuke groaned and put his forearm over his eyes. This is why they never had any alcohol in Sound. It prevented you from doing really stupid shit, like sleeping with the enemy, for one.
Even if it had been good.
... and even if he didn't just think that.
Possibly before or after the previous scene, when he goes to ask Sakura for advice:
"Haseo's good for him, Sasuke," Sakura stated, her back to Sasuke as she restocked a cabinet at the make-shift clinic. "He makes Naruto happy."
Sasuke didn't reply, instead trying quietly not to choke on the drink of water that had gone down the wrong pipe.
Sasuke getting desperate:
"He's..." Sasuke sputtered, trying to come up with something believable. "He's going to rape you in your sleep!"
Okay, so that was anything but believable. But Naruto was stupid, so there was a chance he could convince him....
Naruto paused with his ramen halfway to his mouth, then slowly settled his chopsticks back in the cup. "... No he's not."
"Y-yes he is! He's going to tie you up and rape you in your sleep!" Sasuke breathed out, desperate to come up with anything Naruto would believe now--even if that wasn't definitely it.
"Oh, we already do the tying up thing," Naruto grinned wickedly. "It's pretty hot."
"WHAT. He's going to slit your throat one of these times, Naruto!" Sasuke stared at him in absolute horror.
Naruto started laughing. "You're making shit up, Sasuke. Are you jealous or something?"
"WHAT. NO. WHY THE HELL WOULD I BE JEALOUS FOR?!" Sasuke practically shouted, slamming his palms down on the table and standing up as he did so.
"... Y'know, shouting doesn't make you more believable," Naruto commented with a wide grin. "Especially since you already slept with Haseo."
Sasuke stared at him for a long moment, and then he fell back down into his seat, looking at Naruto dully. "... he told you. And you're not mad."
"Well, I was at first, but Haseo can't hold his alcohol," Naruto shrugged, bringing a bite of ramen to his mouth and continuing to talk as he chewed it (much to Sasuke's disgust). "And he was crying really hard about it, saying he was a horrible person and all that shit. Haseo really does love me, so I had to forgive him."
"...." Sasuke stared at Naruto, his ears buzzing now. "You... You..."
"Besides, I told him that you'd probably end up trying to seduce me once, too, judging by the way you've been acting, so we'll eventually be even," Naruto added, completely unconcerned, as he took another bite of ramen.
".........." Sasuke wondered when he had become so transparent that even Naruto could figure out what he was doing, because there was no way the idiot could've become that smart in three years to rival Uchiha Sasuke.
"That's why you're in my apartment now, isn't it?" Naruto finished his bite of ramen and raised an eyebrow. "I bet you checked Haseo's work schedule and realized he won't be home for another five hours."
"......" Sasuke's brain still wasn't working, so all he could do was continue to stare at Naruto.
"Well?" Naruto raised his other eyebrow, looking at him expectantly as he pushed his empty ramen cup aside. "Going to seduce me now or not?"
Sasuke let out a growl--damn him--and stood, grabbing Naruto's shirt and pulling him half over the table, all in one swift movement, so that their lips met in a bruising kiss and drowned out Naruto's yelp of surprise.
Naruto managed to break his mouth free after a few long moments, fighting back laughter. "Y'know, you could've asked nicely instead of trying to bite off half my--"
"Shut the fuck up and fuck me," Sasuke growled, sharingan eyes narrowed, his face only an inch from Naruto's.
"Okay, okay...." Naruto smiled at him, then brought their lips together again, returning hte bruising pressure.
The aftermath:
Haseo came back early. He took one look at the extra person in Naruto's bed that was glaring at him, then glanced over at Naruto. His voice was almost conversational in tone.
"So he finally seduced you, did he?" Haseo asked point blank.
Naruto grinned in embarrassment, rubbing hte back of his head. "It was more like 'ravished' me, actually. He's not the seduction type at all."
"Figured he wouldn't know how," Haseo stated drying, walking over to the bed and crawling over Sasuke (who was attempting to melt into the mattress) to sit in Naruto's naked lap. "He's Sasuke."
"That's true," Naruto grinned, kissing Haseo's lips. "So, how was work?"
"Pretty good," Haseo replied, kissing back. "So, how was Sasuke?"
"Pretty good," Naruto replied, grinning. "But he's kinda a novice with the sex stuff."
Oh, Sasuke was going to kill Haseo the first chance he got. And cut off Naruto's dick for that matter. 'Pretty good'?! Uchihas were never just 'pretty good' at something!!
"... You just made him mad, y'know," Haseo commented, glancing at the fuming boy still laying next to them.
"I did?" Naruto blinked at Haseo's face, then glanced down at Sasuke, and grinned. "Whoops, you're right, I did."
Uhm, and that's all I have. XD;