Human Behavior 101
by: Mingzhu

A/N: Disclaimers apply. The Naruto characters don't belong to me.
Credits: To HarunoSakuralove-san.. also known as Karma Lord, for the idea of the ending . To the master of lemon-writing! And to SaixSakura! toast

"Why did you bring me here?"

Sai asked the most obvious of questions. The pink-haired kunoichi dragged the art jutsu master into an empty Academy room and forced him to sit in the front row. "I'm going to do you a favor, Sai. There are things you just can't get from books, you know?"

"Why are you doing this for me?"

"Tut," she put her finger to his lips to silence him. "I will be the instructor now, and you will be my student, understand?" She whipped out a pointing stick from out of nowhere. "This is my class, Human Behavior 101."

"I suppose you're bored because Naruto and Kakashi have gone training?" he smiled subtly, watching her redden slightly. When she said nothing, he leaned back against the seat, "Very well.. I'll let you teach me."

Sakura didn't really count on this. Realizing that she was going to be alone with Sai in an empty classroom didn't cross her mind when she brought him there. She should have thought about the idea more carefully. The way he was looking at her with that amused expression on his face wasn't helping. He looked like he was mocking her in some way.

"Ahem.." she cleared her throat. "Pet names. You must have misunderstood me when I said that you call people by their characteristics."

"Is this about Ino then?" his head resting on his open palm.

"No, this isn't only about Ino." Sakura made a low growl in her throat. "Just who's the teacher here anyway?" she whacked him on the head with her stick. "Anyway, you have to be careful with what you say. There are people who take offense with negative words. The usual -san for politeness is always a good start. You can use the word -kun, for your peers, and -chan for those younger than you."

"So.. can I call you, Sakura-chan?"

She hit him on the head again upon reflex. "NO! That's what I'm talking about! You always use them in the wrong way!" there was a deep heavy blush forming in her cheeks. "You use that for people younger than you and.. that's what... lovers call each other. So be a little sensible!"

Sai rubbed his head where she last hit him. This woman was always so confusing. Women in general were confusing. They never seemed satisfied no matter what he did for some strange reason. Perhaps this is why he thought of them as one big mystery and that people were segregated into two categories of species.

People and women.

"All I did was follow what you asked of me."

"You follow things too literally," Sakura said hotly, turning away so he wouldn't see her face so red. Sai continued to watch her, "So.. if by saying.. I become your lover than saying -chan, won't make you hit me?"

"W..what? Who says I want you to be my lover!" she turned around and was about to hit him a third time with her stick when he caught it inches away from his head with his right hand and jerked it forward so she lost balance. His face was now so close to hers, she audibly gulped but her eyes didn't lose contact with his.

"No need to be so defensive, Sakura-chan." he said in her ear, the feel of his breath caressing her skin made her feel strange inside. Alarms were blaring in her head telling her to back off now but her body didn't seem to move at all.

"D..defensive? W..who's being defensive?" her voice came out as something like a squeak. Her heart was hammering and it was echoing in her ears. She couldn't think properly with his hand cupping her cheek. 'Hey..wait, how did he get there?'

A smile curled on the sides of his mouth as he bent forward and kissed her forehead.

Sakura froze as if her entire body was hardening at some point. He lowered his face, feeling his deep breaths touch her eyelids and nose. Her eyes had closed at some point and she felt something warm capture her lips.

Eyes flashed open for a second as Sai tangled his fingers into her tresses. She made a low sound in her throat as she felt his tongue slowly slide into her mouth. He drank that sensual sound and his body trembled in need as he held her there, basking in the knowledge that she wasn't resisting him.

His tongue played with hers feverently, her moans fueling him to continue. His right hand cupped the small of her back and pushed her forward till her knees were supported by the desk as he noticed her uncomfortable position. Lost in sensations, Sakura didn't notice his hand creeping inside her shirt.

When he cupped her breast, her back arched like a cat's. Her voice reduced to whimpering as he rubbed her sensitive peak between his thumb and forefinger through the bra fabric. His lips left her mouth and ravaged her neck the next. "Sai..!"

Another shiver went up his spine with the way she said his name. He pulled at her shorts from below and she was too dizzy with emotions to try to stop him. Somewhere in her head, she was trying to think of a way to hold him back, they were in a public place afterall. What if the students were to..

She felt his fingers rub against her sensitive spot and she gave a soft cry. Sai hissed, feeling his pants start to instantly tighten. Sakura's fingers curled at the corners of Sai's pants. His own closing around her hands as he discarded them. She could only stare in slight bewilderment. Pehaps there was some truth to how Sai used to make fun of Naruto for his..erm.. penis.

She looked back at him, he was sweaty and blushing too. "Do I pass?" he smirked when she blushed some more, covering her mouth with the tips of her fingers shyly. Her other hand had snuck down and grasped him so suddenly, he almost fell off the seat he was using to prop himself up.

Now it was Sakura's turn to smirk as she ran her hand up and down his length feeling him quiver under her touch. To think she had that much power to affect him this way made her feel smug. A hand grasped her wrist to make her let go of him and he climbed on the desk and pinned her arms over her head.

"Do it, Sai.." she begged him, her hips grating against his own and it was driving him crazy. "This will hurt a little.." he fastened his lips to her when he entered her, breaking her barrier. She would have screamed but his mouth muffled her cries. Tears appeared in the corners of her eyes and he let go of her. "I'm sorry..! I didn't mean to.."

"I...I'm fine.. just.. takes a bit of getting used to," she assured him. "Please don't go." Sai shook his head in reply. "I'm not going anywhere." he slowly moved inside her and he could tell that her pain was starting to disappear as she also reciprocated the movement.

Little noises escaped her throat the more they were going. "Faster.. !" she pleaded and he only had to comply. He was getting the best lesson on Human Behavior as of yet. "Come with me, Sakura..." he said as he pulled out completely before delving inside. Her mouth was once again muffled by his own as she screamed her pleasure.

----

Outside, Iruka-sensei shook his head as he walked with Naruto. "I'm sorry. I haven't seen your friends recently, Naruto. Maybe they're training somewhere."

"Aw.." the blonde pouted. He had just finished his training with Kakashi-sensei and looked everywhere he thought they would be. "You're still going to treat me to ramen, right?"

"Of course," he patted him on the head. "Just let me get my wallet, I think I forgot it in the classroom.

"Oh Sai..." sakura murmured happily, currently cradled on Sai's lap, both naked with a blanket around them, on the floor exhausted from their intense love making they just did. Sai smiled weakly in response as he claimed Sakura's lips in a passionate kiss. Sakura cooed contently while Sai's hot tongue battled affectionetly with hers.

Sakura wrapped her arms around his neck and stroked his black hair with one hand. "I love you Sai..." Sakura mumbled into their frantic kiss. Sai groaned. "I love you too..." Sai mumbled between kisses, unaware someone coming into the classroom. "Ah, here's that wallet...oh lord..." Iruka mumbled with surprise and discust while staring at the naked pair under a blanket on the floor.