This starts in the anime episode 8, when Haruhi finds herself in Kyoya's room, and Kyoya attempts to teach Haruhi a lesson.

For the first time in his life, things were not going according to plan. She was supposed to be looking up at him with fear and regret, not staring up at him with curiosity, as composed as ever. "Miss Fujioka, do you understand the position you're in… The power I have over you right now?" He asked her quietly. He was rapidly losing his cool as his body was becoming increasingly aware of said position and power. For once, none of his back-up plans were appropriate.

He knew she was different from other girls, but how could he have underestimated her so badly. And how could he have been so conceited to think he could maintain ironclad control over his baser instincts when he had such a fascinating girl beneath him. He had suspected for some time now that his interests in her were more than financial, but in denial he had brushed these thoughts aside and foolishly proceeded with this plan. Ideas for extracting himself from the situation were quickly considered and discarded.

She finally spoke, "I do understand, Kyoya-senpai."

He didn't think she could possibly guess at the direction his imagination was leading him. It was taking all of his willpower to keep his fantasies at the back of his mind. He was grateful for the dark and the distance between them because otherwise she would have quickly seen or felt the effect she had on him. "If you did understand, I don't think you would be lying there so calmly."

She remained still for a moment, then gently reached for his hand and brought it to rest on her chest. He could feel her heart pounding just as quickly his. So maybe my plan to frighten some common sense into her hasn't been a complete waste. Without thinking his fingertips caressed her collar bone, marveling at the silky softness of her skin. She let out a small gasp. He dragged his gaze from her lips back to her eyes and saw it - what he had missed in his initial assessment of her. There wasn't just curiosity in her eyes, there was trust … and desire. His breaths became more rapid and shallow as he quickly took in the new data. It's not fright that's making her heart beat so fast.

"Do you understand, senpai?" She asked him, eyes searching his face.

He cursed himself mentally because he now knew he was in way over his head. He'd never take advantage of an unwilling girl no matter how good she looked lying in his bed in the moonlight and no matter how much he wanted her. But if he understood correctly, Haruhi wasn't unwilling. He groaned softly in frustration as his gaze swept over her body again. He knew he should abandon his plan right now and take another much needed cold shower, but he couldn't force himself to get up just yet. Plus he needed to compose himself before she became embarrassingly aware of his situation when he stood up. Think cold, calming thoughts. He watched as she prepared to say something, she licked her lips and his control snapped.

"Sen-" She started to question him, but was interrupted by his lips pressed firmly over hers. In an instant they were immersed in heat and the rest of the world fell away. The kiss, which started off almost gently, quickly became more demanding. He bit her bottom lip playfully and let his tongue soothe it. His tongue silently requested entrance to her mouth, which she granted hesitantly. She moaned in pleasure at the new sensation as he explored her hungrily. Time stopped as he felt her tongue begin to dance shyly with his. A part of his mind was screaming at him to regain control of himself, but the rest of him was pleading for more.

He broke the kiss and turned his attention to the soft skin of her collar bone, then her neck. She tastes so damn good. It took all of what was left of his self-discipline to keep from lowering himself onto her completely. He felt her soft hands glide up his arms and shoulders to his neck, and felt her tug him back up for another kiss. She's going to drive me crazy. That was his last coherent thought for the next few minutes as he gave in to her demand and kissed her again. Her hands roamed his sleekly muscled chest and back, unknowingly coaxing his body closer and closer. Her kisses became bolder as she quickly learned what pleased him. Well she isn't the scholarship student for nothing. In a flash, he realized what he was doing and who he was doing it to. Haruhi Fujioka. Scholarship student of Ouran Academy. Member of the Host Club.

He groaned as he unwillingly tore his lips away and sat up on the edge of the bed. They were gasping for air as they stared at each other in the faint moonlight. Seeing her flushed cheeks, kiss-swollen lips, and darkened brown eyes, he knew he would happily sell his soul for the chance to continue what they had started.

Before he could reach for her again, he heard a light tapping on his door. He shot to his feet and Haruhi sat up just as the door began to open.

"Kyoya, you got some lotion? This sunburn is actually starting to hurt-" Tamaki paused as he took in the scene before him. Kyoya stood shirtless next to the bed on which Haruhi was sitting. Tamaki's face darkened with anger, "Kyoya, you -" he was cut off as Kyoya shoved the lotion in his face and left the room, closing the door behind him.

Kyoya sighed and leaned back against the door, listening for a moment to Tamaki's frantic questions and Haruhi's calm denials. He heard the thunder outside and froze. He recalled a detail from a conversation with Haruhi's father. Haruhi was astraphobic. Kyoya turned to re-enter the room, but stopped himself. He knew Tamaki would be able to comfort her, and that he could trust the idiot with her. Tamaki's affections for Haruhi were still strictly paternal, and Kyoya needed time to cool off. He pulled on the vest he had grabbed on his way out of the room, and went to join the others in the dining room.

Not trusting their ability to hide any emotions or reactions from the rest of the Host Club, Kyoya avoided speaking to or looking at Haruhi for the rest of the night and during the ride home the next day, Saturday. She cast curious glances in his direction, but wisely maintained her silence. They would have a better opportunity to speak later.

Sunday morning at the Ootori mansion…

Kyoya stared at the lists before him, the light from his laptop reflected off his glasses as he pushed them back into place. He was exhausted. He had stayed up the entire night analyzing all of the possible ramifications of his feelings for Haruhi. His work had only been interrupted by flashbacks from their brief interlude that left him frustrated and in need of brisk walks. After the events that occurred the night of the beach trip, he could no longer lie to himself about the way he felt for her. The rush of excitement whenever he saw her, the sense of peace whenever she was near, his desire to know everything he could about her. So many signs were pointing to one truth. He never thought he'd fall for a cross-dressing commoner, but she had intrigued him from the beginning. Now he needed to focus on his next goal – making Haruhi his.

According to his analysis, there was very little standing in the way of his pursuing a relationship with Haruhi. Her responses to his kisses suggested she would be agreeable to dating him, so that was not a problem. His data showed he was already poised to buy the Ootori Corporation, so having to gain his father's approval was not a problem either. School was a breeze for him, so according to his calculations, he would have no difficulty graduating first in his class, even after taking into consideration the conversion of a huge bloc of study-time into Haruhi-time. Plus, she would be busy studying a lot anyway, so school would not be an issue. He scrolled down to another list.

The rest of the school still thought she was a boy, but he didn't really care if word of their relationship got out and people thought he was gay. He could easily pay off her debt himself, thus freeing her to reveal her true gender, but he knew her pride would not allow that. He smiled thinking about her stubborn independence, one of the qualities he liked about her despite the trouble it sometimes got her into. She tried to do things herself, rarely relying on others for anything. She was smart, confident, and capable of doing anything she set her mind to. Hiding her gender would not be an issue - as long as he could keep her from confronting beach thugs by herself.

He sighed as he looked at the heading of his last and longest list – The Host Club.