It was probably a good thing that the first time it happened Naruto had been out of the bed, instead standing in front of the Jounin and considering if risking being kicked out butt-naked was a reason good enough to not draw a mustache on Kakashi's face with a permanent marker. Kakashi would cover it with the mask after all, and Naruto only needed the satisfaction to know that there was a mustache there.

So it was a bit of a disappointment when Kakashi awoke, roused out of sleep by Naruto's fixed staring. Shame.

Then, it was Kakashi's turn to stare, fixedly, at Naruto's naked form. And, slowly, frown and form an expression Naruto never thought he'd see his former sensei wearing: utter and mind-blowing bafflement.

"Naruto..." the man slowly said, breaking the long moment of silent and fixed staring that was starting to make Naruto uncomfortable. "Why do you have a pair of breasts?"

"Oh," Naruto said, looking down to see that, yeah, he was sporting a pair of breasts, "that."

"Yes," Kakashi stressed the word, sounding slightly more urgent than before. "That."

Naruto looked at Kakashi, and Kakashi looked back. The silence stretched.

Then Naruto jumped, as if kicked by an invisible being (or an annoyed Kyuubi done with this shit), and blushed. Really hard.

Kakashi would've been able to appreciate the sight much more if it weren't for the developed pair of breasts that had no business being where there had only been a flat chest the night before. He also noted that Naruto's lower regions still held their hanging bits.

"Um, well," Naruto started, looking anywhere but at Kakashi as he scratched his neck. "They, uh...they grow sometimes."

For all that Kakashi Hatake was a certified genius, it took him a long moment of awkward silence to process that.

"They...grow," Kakashi blinked, his brain finally catching up and bursting thousands of questions in a manner much more befitted of a genius. "Naturally?"

Didn't mean it had to reflect in his current brain-to-mouth abilities, though.

This time, it was Naruto who looked at his partner as if a pair of breasts had suddenly grown overnight.

"Yes," Naruto answered, switching his weight from a leg to the other. "It has probably to do with Kurama...you know, being a genderless demon and all that."

"Huh." a blink, another thousands questions being born and dying just as fast in his mind. "It's always been like that?"

Naruto's look was answer enough to that.

"If you mean the breasts, then no, I had to wait till puberty," Naruto scoffed, and Kakashi swore he'd fallen into the most bizarre genjutsu ever. "If you mean my most obvious gender-telling bits changing randomly some days...well. I found out with Ero-Sennin that I can control it, though! if I concentrate enou-and it's not a genjutsu so stop muttering 'kai' and making the hand seals under the blanket, Kakashi!"

"Maa, sorry, sorry," Kakashi apologized, holding his hands up. Apparently reality was weirder than any genjutsu imaginable. "But it is rather hard to believe at first sign, even with such...obvious proof." He waved at the 'obvious proof' sheepishly, feeling still a little lost at the new reality bouncing in front of him.

"I didn't want to tell you like this...I didn't even realize they'd changed," Naruto muttered, crossing his arms and looking away, all but pouting.

And then Kakashi's brain helpfully gave in to the startling realization that this was probably better than any Icha Icha fantasy turned real ever.

And promptly filled with the dirtiest thoughts imaginable.

(He then took the oddest of the Kyuubi's Jinchuuriki's body particularities like Naruto to ramen, as would be attested by any neighbors unfortunate enough to be in or near the building half an hour later. Tsunade surely received enough complains of involuntary and psychologically scarred eavesdroppers to consider smashing the pair's head through the wall.)