Kakashi's first clue is when Sakura bursts into tears in the middle of weapons practice. Not an unusual occurrence in and of itself – but what is unusual is that it's devoid of its usual violent climax. Naruto is all braced for the blow, face all scrunched up on one side and Sakura has her hand raised to send him to the netherworld for the next five minutes – but then she drops her hand, sobs even harder, and turns and runs.
He expects her to be back by lunch, puffy-eyed with wounded pride, but otherwise in proper working order. Except she doesn't turn up for the rest of the day, and instead of showing up bright and early the next day, ready to prove her worth as a fearsome warrior, a note shows up in her place that says she doesn't feel well and not to wait up for her. They're all a little curious, but she shows up the next day and they don't speak about it – or rather Kakashi has the good grace not to ask, Sasuke doesn't care, and Kakashi lobs a tree branch at Naruto's head as he opens his big stupid mouth. Crisis averted and it's back to business as usual.
But then after some time, the same tableau is spread out before him during an exercise about wilderness survival: Sakura, hand raised and teary-eyed, and Naruto curled in on himself and mentally planning how to ice the latest head wound. Kakashi is almost relieved when she wallops him across the face (albeit even harder than usual) and he is all set to get back to the lesson when Sakura pivots on her heel to where Sasuke is snickering and bitch-slaps him across his (completely stunned) face.
She does the whole running away crying thing again and the three of them are left in an impromptu camaraderie of "the fuck?"
Sasuke is still unable to form words, but Naruto says in his usual too-loud-to-be-socially-acceptable voice, "What the hell is wrong with her? She does this every freaking month," and goes off to try and numb his aching skull by dunking it in the stream, but his words echo around in Kakashi's apparently empty skull as he realizes that
a) he is a moron
b) he so did not sign up for this when he agreed to teach these punks
c) shit shit shit
d) he desperately needs help
e) he is a moron
and f) Naruto can never, ever know of this. Ever.
He abandons Sasuke, still shocked stupid and blinking like a guppy, in the woods, and takes off at a run for the medical building. He would drag the Hokage herself with him, but she's too hungover to be of any help, so he grabs Shizune and hauls her to Sakura's doorstep, paperwork be damned. When a red-eyed and completely miserable looking Sakura opens the doors (one hand pressed to her stomach like she's about to double over oh god oh god oh god) he shoves Shizune in front of him and mutters something like "Fix. Her." And runs away.
Sakura shows up to training the next morning with an oddly mysterious look that he chalks up to the glow of womanhood (shudder) and they never speak of it again.
All is well and the world knows peace for about a month before Kakashi starts to notice that Naruto's already grating voice has taken on a habit of cutting out at odd times in conversation and it happens several more times before he realizes that Naruto's voice is cracking because Naruto's voice is changing and that means Naruto has hit puberty and the world is ending.
He's wallowing in his own self-pity during a training session and looking anywhere but the messy-haired youth who is ruining his life when he sees Sakura stop in the middle of an exercise again to adjust her clothes. He's about to tell her yet again that being a ninja takes precedence over looking cute and to buy some clothes that actually fit her when he sees something that looks suspiciously like – no. There's no way. It can't be because he hasn't killed nearly enough people to deserve this, but yes, there's no denying it: those are definitely breasts. And are those -? Yep. Hips, too. When exactly had she gotten those? By whose authority? Sakura wasn't allowed to pull shit like this – the were rules about this kind of thing, for fuck's sake. And if there weren't, then there really, really needed to be. He was going to the Hokage herself to set some guidelines .
He manages to stumble his way to the nearest structure serving alcohol and orders three shots in a row before admitting defeat and just buying the whole damn bottle and attaching it to his face. That's how Asuma finds him when the other shinobi wanders in, looking dazed and exhausted.
"Shit, Kakashi," he laughs tiredly, pulling up a seat, "Someone steal your porn or something?"
"Sakura," Kakashi finally manages after several more fortifying swigs, "she has…" he gestures helplessly to his chest "…and…" more arm flailing. He finally makes a defeated sort of noise and goes back to drowning in his misery, wonderingly idly if he can get a sake IV drip for training from now on.
Asuma's face is ashen as the grin falls right off it. "Oh no. Yours too?"
What can only be cases and cases of a variety of alcoholic beverages later, Kakashi can't lift his head up all the way and Asuma is knocking over beer bottles while gesticulating wildly.
"And she won't just zip up her damn shirts! Shikamaru took a shiruken to the leg the other day because he was too busy staring at them!" He swings his arm around to emphasize his point and a shot glass goes flying. "They'd rather be impaled by sharp, pointy instruments of death than quit gawking at her boobs!" he cries. "It's like – it's like – they're like – Mist ninja!" he exclaims, pointing a finger at the plastered Copy Nin, "'Cause even when I can't see them, I can't freakin' relax because I know they're there, just waiting to come out and attack." Kakashi takes a moment to wrap his mind around equating Ino's chest with enemy shinobi while Asuma begins beating his head against the table and groaning about how he didn't sign up for this.
Kakashi slurs an "I'll drink to that," misses his mouth completely and pours sake all over his pants.
Kakashi isn't the only one becoming painfully aware of Sakura's new…attributes, either. Naruto (squeaky-voiced as ever) is taking more blows to the head than usual from leaving his guard open due to breast ogling and Sasuke (who's suddenly about a foot taller and exactly no pounds heavier, making him look like he hasn't eaten in about two years) has taken more of a clinical observation technique, because Kakashi is beginning to suspect he's actually asexual and will eventually just split in half and repeat like some kind of angst-ridden amoeba to rebuild the Uchiha clan rather than dealing with fun things like hormones and groping.
Sakura herself appears to be in a state of denial until one day she bursts into tears and Kakashi is at least moderately prepared this time or so he thinks until she wails about how she's sorry and she's a failure and how she's getting fat no matter how hard she trains and then it's just a series of heaving breaths and little squeaks and general crying noises and Kakashi is in so far over his head he might as well just drown now and get it over with.
He pats her shoulder awkwardly, trying to assure her that
a) she's not fat
b) she trains just as hard as Sasuke and more so than Naruto (at least these days)
and c) this is all perfectly natural and part of growing up and she's kind of cutting off his oxygen supply, etc, etc.
When it becomes apparent that he is really, really not helping, he drags her off to Kurenai's place, bangs on the door, shoves the tearful pink headed teenager in front of him, and runs like hell for the nearest bar.
Kurenai finds him next to Asuma, sharing sympathy and a pitcher of beer, and slides into a chair at their table.
"I wet through the same thing with Hinata and my boys," she assure Kakashi, all womanly authority and post-post-pubescent confidence. "She thought she was doing something wrong and Kiba and Shino didn't realize what was going on until it was too late," she sighs, and takes a swig from Asuma's glass.
"Too late?" Kakashi asks with a note of panic, tipping forward in his seat.
"Hinata, ah, developed over winter, so she was mostly covered up the whole time. When spring rolled around and she cut back on the layers, Kiba actually accused her of trying to smuggle oranges out of a village we'd just left. Once he figured out that she wasn't involved in a citrus black market…well, he chased her around like a, you know, dog for a week before Hinata got so embarrassed she actually passed out. It's better now that I've talked with them all, but both he and Shino still just follow her in circles when we're off duty. I think they're a bit smitten," she chuckles lowly, and smirks at Asuma who is no doubt reminiscing about his own adolescence and a certain girl he trailed after like a puppy in heat and - oh wait, he still does that.
"Naruto's gonna die one of these days," Kakashi says darkly to his bottle of whatever, "either Sakura's gonna kill 'im or some enemy shinobi is. He's gonna be all" Kakashi waves his arms around for no apparent reason at this point " 'Hi Sakura, are those your illegally smuggled oranges? Let me stare at them like a fucking moron in the middle of a life or death battle, okay?' and then shhhk!" Kurenai and Asuma can only assume this is the sound of enemy kunai hitting the unfortunate boy "and then –" Kakashi smacks his hands together "- dead!"
Asuma nods darkly while Kurenai tries desperately not to laugh at her comrades' lack of comprehension. And sobriety.
"Ino's been using me to practice on," Asuma says after a few minutes of companionable silence and two more glasses of brew.
"Practice what?" Kakashi asks in horror, spilling beer on himself in the process.
"Everything," he replies with a shudder. "Pick up lines. Flashing her legs and...stuff," he buries his head in his hands and groans, "I've ended training two hours early for the past three days just to escape." Kakashi glances at Kurenai's leg holster and thinks that Asuma (or rather, Ino) is damn lucky that she's secure enough in her own curves not to be threatened by the blonde's. The kunoichi giggles, in fact.
"I pulled the same thing with my sensei," she laughs, and settles against Asuma's shoulder. "You're someone safe to test out her new equipment on. She'll get over it once she realizes it's more fun with actual results."
Asuma does not seem comforted by this. In fact, his face gets even darker as he contemplates it. "If anyone touches her, I'm gonna kill 'em and make it look like an accident," he states soberly, and Kurenai smiles at him and kisses his cheek.
They've settled into a companionable (on Kurenai's part) and traumatized (on Kakashi and Asuma's) silence when Gai shows up, demanding to know the cause of their darkened youthful spirits. Kakashi gives him the abbreviated version and cringes at both the proximity of the green spandex and the too, too loud for his piss drunk ears guffaws, then tells him to take a good look at Tenten tomorrow at training.
The next night Gai is at their table, weeping uncontrollably and mourning the tragic beauty of the grace of womanly youthful energy. Kakashi pats him on the shoulder and hands him a beer.
A/N: This was originally going to be a longer KakaSaku onshot, but I'm a sucker for harmless and completely inept mentor fun. However, would anyone be interested in a follow-up of a KakaSaku-esque nature? I'll probably write it anyway, but I'd like to hear your thoughts.