After the sex, Kushina kicks them out.

"Okay. You can go now and, hopefully, the lesson is learned." Said Kushina, now fully clothed, to a male Naruto, who only responded with a sheepish and uncomfortable grin.

Sasuke, slightly offended by the dismissal, simply shushined away as Naruto's eyes tried to follow him with yearning and a rueful gaze.

"Now, go to your room and think about what you did, Naruto. I need to work on some seals and should not be disturbed. You may go as well."

And thus followed many days of intense masturbation from Naruto, both as a boy (never a man) and as a girl, in which he thought nonstop about his mother and Sasuke.

And, as the days stretched, and he didn't see the Uchiha a single time, Naruto had to admit, if only to himself, that, between him and his mother, he may be thinking about Sasuke slightly more.

Luckily, some of his masculine smell still lingered on Naruto's nose and wrists, where the girl had surreptitiously rubbed the underwear. Of course, he had to be careful in the shower not to spoil it, but it was totally worth it.

It was Sasuke's mark.