Later, neither of them will know how it had happened. Later, they will argue about it. Later, they will sneer and snipe and attempt to assign blame.
Later, they will remember.
Later, Jou will creep through his bedroom window, lie in his bed, listen to his father snoring and remember. He will clench his fists in the sheets, and pretend it's the other's collar he is grasping. He will recall dry lips and blue eyes, and had that been a hint of a sparkle in the azure depths?
He will allow himself to dream, just for a moment, of what could be. Of seeing that mocking mouth curl upward, just a bit; of those eyes losing some of their diamond hardness. Of finding security in another person, and having someone to run to when he has to run away. And then his father will grunt in the next room and roll over, and Jou's dreams will fall away, and he will shake himself and think What the hell is wrong with me?
And he will very carefully never admit that he might have liked it.
Later, Kaiba will sit in front of his computer, and attempt to get something done. He will stare blankly at the screen, and try vainly to keep away the memory of the surprise in the blonde's eyes, surprise that perfectly mirrored his own; try to keep from recalling the softness of the other's hair where it fell in both their faces and brushed against his cheek. He will clench his teeth until his jaw hurts, and will away the unwanted feelings stirred by the incident.
He will not allow himself to imagine what it could be like. He won't permit himself to fantasize about shared laughter (how long has it been since he laughed with someone?), about someone other than Mokuba to talk to (his brother is still so young), about the simple comfort of human contact (though he shouldn't need such a frivolous thing). He will creep down the hall, and open the door, and look on his brother's sleeping face. Making sure, as he does every night, that Mokuba is still there, still safe. He will look for a good long time, to remind himself why he cannot allow anything--and especially not anything with blonde hair and an insatiable appetite--to invade their lives. It's too dangerous to let someone else in.
And he will carefully lock away all thoughts that do not deal with the running of the Kaiba Corp empire, and go back to work.
But that is all later.
At this moment, they will sigh and give in, for only a moment. They will not be Jou and Kaiba, who are far too different. They will be Katsuya and Seto, who are just two people.
And they will pretend that it isn't wrong, never knowing that their fable could so easily be the reality, if only they would allow.