Disclaimer: I do NOT own Naruto.

Understanding Emotions

Itachi Uchiha liked the army. There was no other way to put it.

He liked the way the men all walked in ranks. The way the men all knew their places. He liked the symmetry, the perfection that could only be found in barracks. He liked the unspoken etiquette, and the drilled in respect for superiors. He liked the discipline and the obedience.

But at the same time, the young Field Marshal liked to watch the men break ranks at the end of the day and goof around together. He liked to watch them relax, to stop being killing machines and start being people.

Which was why his newest General frustrated and confused him.

Itachi had never approved of taking children and training them to be soldiers. However, Konohagakure Army had a division entirely made up of troops just like that. Almost a completely separate force, Root was an odd group, mostly made up of soldiers that had been in military school since a young age.

Their newest General was a prime example of that.

Orphaned and alone in a war-torn country, he had been taken into the army based and raised by the priest who ran the chapel there. It was supposed to be a temporary arrangement, but the war continued for five long years until the priest sent the boy away to stay at a base that was not in the war, afraid for his safety.

The boy was found by Danzo, the previous general of Root. He was trained ruthlessly, and had little to no childhood. But the time he reached eighteen he was the perfect soldier, a killing machine.

After Danzo's unfortunate demise the boy was raised to General in his place. As Itachi was in control of the entire army, he kept all his General's close. This included the new one.

But Sai was a puzzle he had never come across before.

Itachi was an Uchiha. The Uchiha's had a proud history of decorated war heroes. Their sons were raised to be tough, or were sent away so as not to draw attention to themselves. Rather like Itachi's own brother, Sasuke, who had chosen to be a musician rather than pursue the expected military career. Their father sent him faraway to Iwa, the city of music, where he stayed out of sight and out of mind.

The Uchiha's were a proud family. They rarely displayed obvious emotion, but the smallest movement on their attractive features spoke volumes. When Itachi raised an eyebrow it could mean he was either mildly amused, or hoping whatever General had screwed up had a damn good excuse for fucking up. A smirk could mean he was pleased, but it could equally mean he was about to rip coldly into someone, cutting them to the very core. A narrowing of the brow meant that Itachi was annoyed by the news he received, or angered.

And calm nothingness either meant he was filled with icy rage and waiting for an unsuspecting bystander to unleash it on, or he was deep in contemplation.

Few ever learnt to read Uchiha emotions. But the emotions were there.

With Sai, they weren't.

The odd man had ordered a dozen of his troops into a potentially life-threatening situation without batting an eyelash, but Itachi had found him wearing the same expression as he crouched beside an injured bird, coaxing it into a box. Sai looked exactly the same when attending a burial or enjoying a glass of wine with the other high rank officers late at night.

He was completely emotionless.

Itachi wanted nothing more than to see that face twist with rage, pleasure, sorrow or fear. He wanted to see those stunningly perfect features show an emotion other than polite blankness. He wanted to see something.

Itachi had tried being ice cold to him. He had tried being as warm as an Uchiha got. He had tried belittling Sai, or inflating his ego. Nothing worked. No reaction.

And it was beginning to piss the Uchiha off.

--

"Sai, what on earth are you doing?"

Itachi should have been more shocked to find one of his General's crouched in his closet, head pressed to the pant leg of his uniform, after his evening shower, but somehow the fact that it was Sai seemed to take away from the shock.

"Good evening, sir," Sai greeted him with a quick salute. "Please, go about your business. I am merely conducting an experiment."

"Hn," Itachi stared at him a moment more as Sai returned to the clothing before he turned on his heel and slammed the door shut.

--

"Sai, what on earth are you doing?"

Itachi had to admit, this was a lot less weird than finding Sai in his closet. Still, the man should not be sitting atop the shelves in his office. How in hell did he even get up there? And how little did he weigh if the shelves weren't falling over?

"Good afternoon, sir," Sai gave the appropriate salute. "Just my experiment. Please, pay me no attention."

Itachi eyed him for a moment before he dropped down behind his desk and began to work. His eye twitched as Sai moved like a monkey across the room to land on the filing cabinet, but he didn't say anything.

Only after Sai had gone over every inch of the room, including the gap under Itachi's desk, did he leave with another salute.

--

"Sai, what on earth are you doing?"

Itachi was going to have to call in the base head shrink to find out what the hell was going on with his general. Sai was now tearing his food apart, adding small titbits to various beakers filled with odd coloured liquids.

"Good morning, sir," Sai nodded as Itachi set down his tray of food across from him. "Just my experiment. Please, ignore me."

Itachi could only eat half his breakfast as he watched Sai tear up his food and submerge it, carefully noting the result.

--

Itachi was on guard from then on. It was obvious Sai was following him, but Itachi decided to let it slide. Having the gorgeous man's attention on him wasn't bad at all. If only he would come close enough for Itachi to do something about that. Instead he hovered away from him, darting off whenever Itachi looked his way. It was frustrating and incredibly annoying.

Fed up at last, Itachi cornered Sai. He managed to pin the other man against the wall, his arms forming a cage around him.

"General Sai," he growled. Sai met his eyes calmly. "May I enquire as to why you are following me?"

"Oh, Field Marshal Itachi," Sai smiled one of his wide, fake smiles. "Of course you may."

Both men waited patiently until Itachi narrowed his eyes and growled softly.

"Why are you following me?" Itachi snapped. Sai's fake smile wavered.

"Following you? Is that what you think?" he asked. "It's just a coincidence."

Itachi's eyes darkened and he leaned in closer, pressed his face to the curve of Sai's neck. He couldn't resist inhaling the scent of the man's clean skin.

Sai stiffened completely before he managed to duck out from under Itachi's arms and vanish. A deep frown etched on his face, Itachi watched him go.

--

"Sai, why are you still following me?"

The general was good. He was very good. He wasn't the leader of Root for nothing. But he was nowhere near as good as the Field Marshal.

"Following you, sir?" Sai dropped casually into a crouch beside Itachi from his hiding place overhead. "It's just a coincidence."

Itachi's eyes narrowed as he stopped walking entirely. Sai stared up at him with wide, pure black eyes. Itachi stared back down at him, never one to drop eye contact, and couldn't help but lean in slightly. Sai's head tilted up, his slightly pointed chin pointing towards Itachi. The older man couldn't resist raising a hand to cup that pale face, stroking his thumb over soft skin.

Sai's eyes increased in size before lids fell down to cover them. He took a slow deep breath and pressed his face to Itachi's palm.

"This feeling..." he whispered, almost to himself. "I don't understand it."

"What feeling?" Itachi murmured as he stroked Sai's face. "Tell me what you feel."

Sai's eyes snapped open and he stepped back instantly. His hand flew to his pocket and, ignoring Itachi completely, he pulled out a small notebook and began to scrawl something down.

"Sai?" Itachi stepped closer to him. "What-"

"Excuse me, sir," Sai flashed a wide fake smile. "I have business elsewhere."

And then Sai was gone, leaving a frustrated Itachi behind.

--

Itachi was an extremely patient man. He had an iron will that never wavered. He could deal with the most annoying people and still be calm. He was immovable.

But Sai pushed him to the limit. And he finally snapped.

Abusing his authority for the first time, Itachi called Sai to his office. The man had to obey, of course, and Itachi was standing right behind the door when he entered.

As Itachi pushed it close, Sai's training took over. He whirled, dropping into a crouch as a knife slid smoothly into his right hand. Itachi locked the door before raising an eyebrow at the man on his floor.

Sai straightened, sliding the knife back into its hiding place and saluting. "Sir, you summoned me?"

"Yes," Itachi moved swiftly towards Sai, who backed away. "I did not give your permission to stand at ease."

Sai snapped to attention. His heels came together with a sharp click as he stood straight, eyes meeting Itachi's squarely.

"Sir!"

"You've been insolent lately, Sai," Itachi said as he began to circle the other man. "Speaking back. Slacking off. Haven't you?"

"Sir, I respectfully dis-

"Haven't you, Sai?"

"Yes, sir."

"And slacking off is wrong, isn't it Sai?"

"Yes, sir."

"So you need to be punished, don't you, Sai?"

"...Yes, sir."

"Hn," an evil smirk slid onto Itachi's face. "I'm glad you see it my way. Follow me."

Itachi stalked past his desk to his chair and wheeled it around to sit in it. Sai paused before him, eyes asking a silent question. Itachi's smirk grew and he spread his legs wide.

"So, Sai," Itachi's voice was barely above a whisper. "Now is your chance to make up for your misdemeanours. Earn your right to be back in my good graces."

Sai's mouth narrowed into a frown, barely there, and Itachi raised an eyebrow.

"Sir, you are abusing your position," Sai's voice was cool. "And I find it makes me feel very uncomfortable."

"Hn," Itachi smirked. "And what are you going to do about it?"

Sai's eyes widened briefly as he realized that Itachi didn't care. Itachi didn't care that he was doing wrong.

"Now," Itachi loosed his tie. "I want you to tell me why you are following me. And what your experiment was."

"I was following you, sir, because I don't understand," Sai said in a flat voice. "I don't understand why my body reacts the way it does around you. Hence my experiment. I want to know why my heart speeds up when I look at you. Why my chest feels heavy. Why my breath is hard to draw in. I don't understand it."

"And you want to understand?" Itachi knew his eyes were bright with lust and desire, but he didn't care. "You wish to understand these emotions?"

"Yes," Sai closed his own eyes. "More than anything."

"Hn. So be it."

Itachi reached forward and grabbed Sai's hand. He tugged the surprised man forward until he was forced to straddle Itachi's lap as the Field Marshal's arms slid around him, holding him tight to his chest.

"Is your heart speeding up?" Itachi whispered. "Is it painful?"

"Yes," Sai breathed against his neck. "It hurts. I don't know why."

"I do," Itachi buried his face in Sai's dark, soft hair. "And I can tell you why... but nothing is for free."

"What do you want?"

Itachi's smirk was pure evil as he tilted Sai's chin up. "A kiss. All I want is for you to give me a kiss."

"A kiss?" Sai sat back on Itachi's lap to look at him. "One kiss, and you'll answer my questions?"

"Mmhm," Itachi pressed his face to Sai's neck again, inhaling deeply. "Just... one... kiss."

Sai seemed to be contemplating it as he stared down at Itachi. Itachi ran a hand along his neck and titled his chin down. He drew the other man in, meeting no resistance.

"Sir..." Sai whispered just as their lips met.

Sai was still tense in Itachi's arms, so the older man moved slowly, pressing his lips softly and teasingly against Sai's. He nipped at the perfect pale mouth until the rigid man began to relax and kiss back. Itachi slid his tongue gently into Sai's mouth, and tightened his arms around the man when he jumped slightly.

Sai let out a sudden moan and melted forward against Itachi, hands sliding up to grip dark hair. Itachi pulled him closer, wanting to devour the sweet man, wanting to taste him, and make him feel.

Sai was very responsive for a usually expressionless man. He was writhing in Itachi's lap as the Field Marshal grabbed his ass and drew him in, rocking the other man down onto his covered erection. Sai gasped and moved closer, his hands gripping Itachi's hair until it was almost painful.

"S-Sir!" Sai whispered as Itachi finally allowed him to breathe. "I-I don't understand-"

"Your heart is beating faster," Itachi nipped at Sai's neck softly. "You're erect. You want me."

"I've experienced lust before," Sai tilted his head back all the same, allowing Itachi to suck on his throat. "This is nothing of the like. I have an overwhelming desire to stay by your side. To be with you at all times. When your hair falls into your eyes, I want to be the one to push it away. When you fail to eat, I want to bring you food. When you sit all alone, I want to come keep you company."

Itachi paused in his exploration of Sai's neck and sharply pulled the other man's chin down so that he could look at him. He pressed a soft kiss to Sai's lips and cupped his cheeks.

"Does this make your heart beat faster?" he whispered as he pressed soft kisses to Sai's cheeks. "To know that I want you to do all that? I want you to be the one who takes care of me when I neglect myself? To be the only one allowed touching me so familiarly? To be the only one I want to hold close and never let go?"

"Yes," Sai breathed. "This excites me more than our previous activities."

"I thought so," Itachi grasped Sai by the back of his neck and drew him forward until the other man's face was nestled in his throat. "These feelings of yours go beyond lust. I would not yet call them love, but the potential is most definitely there."

"Love?" Sai sat up straight, eyes boring into Itachi's. "You believe I will fall in love with you?"

"Yes," Itachi drew Sai back down. "And I will encourage this any way I can."

Sai remained pressed against him for a long moment before Itachi felt him slowly pressing gentle, hesitant kisses to his neck. He leant back further in his chair, and Sai looked up, meeting his eyes squarely.

"Sir, because we have discovered these emotions I feel does not mean we should stop our previous activities," he said as he reached forward and began to deftly unbutton Itachi's uniform. "I favour being the submissive partner, but I am not opposed to switching. I prefer to feel my partners inside of me, and quite often masturbate with fingers up my-"

Itachi swung the chair around and leapt forward at the same time, pinning Sai between his body and the desk as he hungrily devoured the other man. Sai's hands dug back into his hair, and the man gave a soft tug. Itachi groaned at that – his hair was very sensitive.

"Don't stop," Sai whispered as Itachi returned to ravishing his throat. "Please. My body couldn't take it if you stopped now. It needs release."

"I don't plan on stopping," Itachi growled as he stripped his outer jacket off. Sai's fingers danced down his shirt, undoing the buttons and helping Itachi take it off. As soon as he was naked from the top up, Itachi began to tear at Sai's clothing.

Sai shifted until he was sprawled out on top of Itachi's desk, the Field Marshal tugging his pants, shoes and underwear off. His socks soon followed. Sai pulled off his jacket and tie, but only managed to unbutton the shirt before Itachi was on him, sucking a nipple into his mouth.

Sai's back arched beautifully, and Itachi reached up to grip his waist, teasing the soft skin with caresses. Sai's body was lean and slightly muscled; the body of a fighter trained to blend in with a crowd. It was a sharp contrast to Itachi's obvious muscle.

"Sir..." Sai's hands found Itachi's hair once more, and he tugged hard. Itachi looked up at him and smirked.

"You may call me Itachi, Sai," he murmured as he blew on the erect nipple before switching to the other.

"I-Itachi..." Sai seemed to taste the name, as if he was saying it for the first time. "This is stimulation like I have never felt. I... want more."

"You'll have more," Itachi whispered. "You'll have everything."

Itachi slid his hands down from Sai's waist to his thighs. He gripped them and drew them apart as the other man reclined completely on the desk. Itachi leaned down, straight past Sai's erect cock, to nip at Sai's pale thighs. Sai let out a long, deep breath as Itachi sucked up a couple of hickies.

"More," Sai whispered, unable to hold back the word. He slid a hand out of Itachi's hair to cover his mouth, but Itachi didn't like that. He reached up and grabbed Sai's hand, tugging it down before he lifted his head up.

"You can ask for anything," he murmured. "Don't be afraid."

"Please, more," Sai whispered. "I want more."

Without warning, Itachi took Sai's cock into his mouth. The pale man gasped, arching up and moaning softly as his hands grasped soft locks. Itachi bobbed his head and sucked hard, wanting to take the edge off so that Sai was more relaxed.

Sai tugged hard at Itachi's hair, and the man looked up, straight into lusty black eyes.

"Fingers," Sai managed to mutter. "Now."

Itachi smirked as he reached down into the pockets of his trousers and withdrew a tube of lube. He uncapped it as Sai watched and squirted the substance over three fingers. His smirk firmly in place, Itachi lowered his fingers to Sai's twitching entrance.

Sai let out the most beautiful moan as Itachi slid a finger straight inside of his body. He clamped down on Itachi, causing the man to hiss and add another finger. He thrust his fingers, stretching them apart and widening Sai's entrance. Sai writhed on the desk, knocking things off left and right.

Itachi couldn't resist adding another finger, and he smirked as Sai reached out for him, arms waving until Itachi fell forward, kissing his lips softly. Sai let out a light moan against Itachi's lips as he wrapped his arms around strong shoulders.

As soon as he believed Sai was properly prepared, Itachi withdrew his fingers. Itachi reached down and unbuckled his pants, pulling his heavy erection out. He squeezed more of the lube out of the tube and coated his cock quickly.

Sai sat up suddenly and then slid of the table. Before Itachi could ask what he was doing, Sai turned to show his back to Itachi. Itachi smirked once more and wrapped his arms around Sai's waist, nuzzling his dark hair. He pressed forward against Sai's ass, rubbing his cock against it teasingly. Sai reached back and grasped a handful of Itachi's hair.

"Now," he whimpered. "Fuck me."

Itachi couldn't resist that. He bent Sai forward onto the desk, and knocked his legs apart. Sai grasped the far edge of the table, and glanced back over his shoulder. Itachi lined himself up with Sai's entrance and smirked and pushed forward.

Sai gasped loudly, his back arching as Itachi slid into him. He squirmed on Itachi's cock until firm hands grasped his hips and held him still. As soon as Itachi thought Sai had waited enough, he thrust forward hard, pushing Sai further onto the table.

Sai gripped the edge of the desk hard as he pushed back on Itachi. The older man could see his knuckles were white as he held on, gasping and moaning as Itachi drove into him.

Itachi leant over Sai's back and pressed his lips to a pale shoulder. He sucked until a hickey appeared, before moving down slightly, and sucking again. All the while his hips thrust into the tight heat that was Sai's ass.

Sai moaned lowly, and Itachi paused, straightening up. He thrust hard again, and Sai let out another loud moan, twitching on the desk. Itachi had hit his prostate.

Itachi let loose the last of his control. His hips thrust wildly, slamming the desk forward until it was skidding along the floor with the strength of their fucking. Sai's moans were getting louder and louder, much to Itachi's delight. He wanted to hear Sai scream.

"I-Itachi!" Sai cried. "S-Sir!"

"More," Itachi hissed as he slammed in. "Speak to me, moan, scream, let me hear you!"

"Sir!" Sai's head was thrown back, his hair sweat soaked and his skin glistening. "Please! More!"

Itachi gripped Sai's hips harder, hoping he would leave bruises in his skin. He wanted Sai marked. Sai was his.

Itachi reached down and gathered up Sai's dripping cock. He stroked it fast, working them both towards their orgasms. He wanted to feel Sai clench around him, feel him explode all over his hand. The heat was rising inside of him, and he knew that as soon as he completely claimed and marked his man, he would not let him go. His Uchiha over-possessive side was kicking in.

With a loud, wailing moan, Sai burst beneath him. He bucked beneath Itachi, rocking the entire desk. Itachi couldn't starve off his own orgasm, and bit down on Sai's shoulder as he came, thrusting a couple more times.

Sai was panting heavily as he gripped the desk as best as he could. Itachi ran his hands down Sai's back before he sat back in his chair. Sai peeked over his shoulder at Itachi, who raised an eyebrow at him. Sai straightened and turned to face Itachi, who let his eyes drift down Sai's naked body.

Sai straddled Itachi's lap shamelessly, wrapping his arms around the Field Marshal's neck. Itachi drew him in for a soft kiss, running a hand through Sai's mussed hair.

"So, do you understand now?"

"I think you might need to explain it again, sir."