The first time it happened, Kakashi would swear it was an accident. In fact, he might even go so far as to deny it even occurred in the first place. He definitely did not lock lips with his student, not at all, not ever. He wouldn't, for regardless of his inner perverseness, he prided himself on being proper and respectful. He was Hatake Kakashi. He was sensei to the two saviors of the world, he was advisor to the hokage-in-training, and he was leader of the dog summons. He was honorable, respectful, and very fearful of retaliation from a certain blonde Sannin with far too much strength in her fists.
So, when his darling student tripped and stumbled over her own feet, he blamed what happens next on the fact that he could not override his instinct to catch her in her descent. He paid no heed to the ground that was freshly laden with rain, they were some of the most revered ninja in Konoha and they did not lose their footing in mud. They were trained to walk on water, it was infeasible to even humor such an idea. Or so he thought, because the blonde jinchuriki was in his arms and his feet were sliding and Kakashi damned every ounce of water in existence as he fell backward. Silver hair turned brown as a wave of earth overwhelmed the both of them, but that was the furthest thought from his head. One wide grey eye met two cerulean ones in shared disbelief as petal lips graced the masked ones of his own. He absolutely did not notice how soft her body was against his nor did he acknowledge her warmth, and Hatake Kakashi did not revel in the moment long enough to linger. He did not, because that was improper, and the hokage-in-training was too dignified and too innocent and too damn young to be in this situation with him.
He would deny any of it until the day he died. However, when her tan skin flushed a becoming rose color, he might own up to the fact that she was beautiful. He was taken aback by the situation, enraptured by the woman pressed against him. The sun had gilded her hair to the point of it shimmering as a frame of gold curtained around them. It was almost too much, he decided, and any man with any decency would be ensnared by her. He was helpless really, just a victim of circumstance. So when he did not immediately remove himself from the situation, he chalked it off to helplessness. When his hands settled upon her waist, it was only to help lift her from his person. And when his grey eye closed, it was only because there was mud in it and not at all because the woman before him was too radiant and he found himself blinded.
When said blonde recovered from the shock and all but leapt up and away, so far away, from his person, Kakashi did not mourn the loss of his darling student. Rather, he merely dismissed the situation as accident and bemoaned the mud hardening upon his vest. He certainly did not miss her warmth as it ebbed from his skin, nor did he sigh because he was stricken with a ghost of longing. It was indigestion, he decided, from laying down too quickly after eating. And when his red faced student shook her head as if she could dispel the memory, he did not find her endearing.
Hatake Kakashi dusted off what he could, made a quip about her owing him a new vest, and substituted himself out of the way of the ensuing roundhouse kick that would have knocked his teeth in. He acknowledged the wood as it splintered in his place, threw a half hearted wave over his shoulder, and disappeared from the scene entirely. It would be two days before he returned to his post by his student's side at the hokage desk. It did not go without notice how her cheeks tinted at his proximity, but if their fellow comrades had any questions about such a circumstance, they knew better than to voice their curiosity. Besides, Hatake Kakashi would deny anything that transpired on that fateful day and his student had fists quicker than Tsunade's.