Uchiha Sasuke was twenty-one years old when he finally decided that yes, he was in fact, gay.
He came to the conclusion one evening while taking a break from studying for the upcoming exam period. Naruto was lying on his back on Sasuke's bed, eyes closed and headphones over his ears. Sasuke idly watched the blonde's leg pop up and down along with the beat of the music. Usually the Uchiha demanded on absolute silence whilst he was studying. Thus, he concluded, the fact he not only tolerated Naruto's presence in his room at the moment, but also allowed him to be humming as well, was very heavy evidence on the behalf of him being infatuated with the blonde idiot.
Sasuke contemplated over his newly realized feelings for his best friend for a moment, tapping his pencil against his lips in thought. Then he did what every self-respecting young Uchiha did when faced with life-altering realizations.
He acted upon it.
Naruto opened his eyes when he felt the mattress dip under. He took the headphones off: certain Sasuke was climbing over to say something. Instead, Sasuke scooted over and just plain kissed Naruto on the lips.
Sasuke ignored the inevitable spluttering that followed the initial shock and just pressed in further. He stopped Naruto from flailing by grabbing his arms and pressing them against the mattress. Naruto opened his mouth to protest vocally and Sasuke gleefully dipped his tongue in. Naruto let out a shocked whimper as their tongues met, his whole body jerking. Heat twisted in Sasuke's gut when Naruto's tongue didn't shy from the touch but pressed back to brush against his.
Both were panting when their mouths finally separated. Naruto was thoroughly flushed while Sasuke steadily grew aroused.
"What the FUCK was that?" Naruto roared as he caught his breath.
"Idiot," Sasuke replied.
"Wh- what the hell you think you're doing? You- you-" Naruto yelled, face burning red and expression resembling that of an angry bullfrog.
"You're still as dim-witted dead last as ever, so I thought I should let you know that-"
"What the fuck? First you start tongue-fucking me and then you insult-"
"Shut up, I wasn't finished," Sasuke interrupted, a smirk beginning to tug at his lips. He noted how he was still laying on top of Naruto and yet not sporting a black eye, which only went to prove his point. "You and I are most probably already in love, or at least about to get there."
"Bw-HUH?"
"So seeing we will inevitably end up as a couple-"
"WHAT?"
"-I thought it's for the best I make my affinity for you clear at this stage, just to save time and further embarrassment."
Naruto opened and closed his mouth like a fish for a long moment, staring at Sasuke like he'd suddenly grown an extra head. Sasuke stared back, feeling slight pity for the poor, unsuspecting fool.
"...You're completely off your bonkers," Naruto concluded incredulously.
Sasuke grinned. "I must be. Otherwise I'd never fall for an idiot like you."
Then he made Naruto splutter some more.