Disclaimer: Naruto belongs to Masashi Kishimoto. This non-profit, non-copyright infringing fanfiction belongs to me under international copyright laws and taking it is plagiarism. Don't steal and don't sue. Thank you *Phantomness bows*

Warnings: Explicit mentions of female biology

Chapter 14: Growing pains

Most kunoichi did not start their menstrual cycles until late. This was due to several factors. Whether through harsh training, such as Hinata and Tenten, or dieting in order to impress Sai and Naruto, such as Ino and Sakura, respectively, they simply did not have enough body fat accumulated for their bodies to decide they were biologically ready to give birth. These girls did not have Uchiha Mikoto for their mothers. While Sasuke had the harsh training part down, he also had his mother watching every bite he took at home when he ate a meal. And if he missed a bite and said he wasn't hungry… well, even without her Sharingan active, it had only taken one instance of Uchiha Mikoto giving Sasuke a look and putting an extra large portion of beef with vegetables on Satsuki-chan's plate to curb that tendency. And just to make the lesson sink in, there had been no tomatoes for a week.

Sasuke, who still thought of himself as male, despite being in a female body, knew that he was going through some changes. Yes, he had started to grow breasts, and yes, they were irritating. He had to adjust for their presence on his chest, but at least he had not sprouted them overnight. And, fortunately, Uchiha women were, as Uchiha men were, built for speed and did not have what Sasuke considered enormous hindrances. And Uchiha Mikoto, being a good mother, had not said a word and instead gotten her daughter several modest sports bras in black and dark blue, although with little embroidered uchiwa on the back, as was expected.

However, when Sasuke woke up, feeling blood trickling down his thighs, he naturally assumed the worst. His eyes snapped open, Mangekyo Sharingan and Rinnegan scanning for enemies. There were none. Kiba and Akamaru were still on guard. They were awake. They were alert. This was not a genjutsu, and if it were someone who could cast genjutsu that could not be broken by his eyes, someone who had gotten past both him and Itachi… He felt fear for the first time in a long while, and he had to repeat to himself not to panic several times, mentally counting backwards from ten to one, making sure his hands were steady as he checked himself for damage in that intimate area.

It was odd. He was sore, yes, and he was still bleeding, but how was he to cauterize and seal off this wound? Applying pressure was out of the question… Sasuke found the medical kit he always had in his pack and bandaged himself as best he could, before flickering to Itachi's tent. Fortunately, Itachi had already felt his slight flare of chakra and was awake.

"Satsuki, what is wrong?" Itachi questioned with a slight look of concern in his eyes. He knew his younger sibling would not wake him for a trivial matter.

"I am bleeding… here." Sasuke said, gesturing. Itachi blinked, slowly, his eyes widening slightly. He realized with a sinking feeling that the academy teachers had clearly neglected an important part of health education. He felt sweat start to gather in his palms. He wished his mother were here to explain. Unfortunately, she was not, and as both Satsuki's elder sibling and jounin-sensei, it fell to him.

"I did not engage in intercourse." Sasuke said, as calmly as he was able. "The academy teacher mentioned that it is natural to bleed a small amount when one first engages in sexual relations with a member of the opposite sex."

"I believe you," Itachi replied, not wanting to even think about his younger sister engaging in any sort of sexual relations. He was frantically trying to remember everything he had learned about women, which, unfortunately, seemed to be fleeing his mind at the moment. His precious younger sister was bleeding and he could not help her, and they were on a three week long B-rank mission to survey the Forest of Death.

After a moment's hesitation, Itachi formed the familiar signs for a shadow clone. As Sasuke watched, it flickered away. There was nothing else they could do for the moment, but wait.

Itachi's shadow clone thoughtfully disguised itself before entering Konoha proper and the nearest convenience store, heading for the aisle marked feminine products. Then, it hesitated. The array of products was frankly, mind-boggling. There were sanitary napkins of all shapes and sizes. There were tampons, meant to be inserted inside the body – Itachi tried vainly to banish the mental image of Satsuki putting something inside of herself. There were menstrual cups. There were even diapers – hopefully Satsuki would not need those. His eyes fastened on the one item he did recognize, and that was when he registered, too late, a familiar presence behind him.

"Itachi," His mother's voice said, very calmly, but only a blind man would have failed to register the threat in it. "Why are you looking at condoms?"

"Please do not hit me, mother, I'm a clone." Itachi said as quickly as he could. "Satsuki is bleeding."

"Bleeding," Mikoto frowned. "Itachi, Satsuki is a medic-nin. She knows how to deal with injuries."

"Not normal bleeding," Itachi clarified. "She is bleeding between her legs." He gestured to his crotch, trying and failing to suppress the blush on his cheeks.

Mikoto sighed. What were they teaching the children at the Academy these days? Then, she remembered that Itachi had graduated from the Academy at age seven, and Satsuki's area of expertise was basic medicine, not gynecology. In fact, now that she thought of it, most kunoichi did not start menstruating until later in life…

"Here," She said, starting to grab packages off the shelf. "I'll give her the talk about menses when you two come home from the mission. She'll need these green ones during the day and these thicker orange ones at night. Tell her to change the green ones every few hours before they soak through. The moderate strength painkillers in her first aid kit will do fine if she's in pain. Oh, and bring her some of this." Mikoto said, tossing Itachi a few more packages.

Itachi caught the last of the packages. "You're sending Satsuki underwear and chocolate?" He asked dubiously.

"Trust me, she'll need it." Mikoto said, with a mother's knowing smile. "Now hurry back!"

A few minutes and body flickers later, Sasuke, now introduced to the wonders of having a menstrual cycle, having taken a painkiller and changed into clean underwear and an overnight pad, was trying to go back to sleep. It was not working. Finally, he decided he would sleep better in Itachi's tent, so he packed up his sleeping bag and went to join his older brother. Itachi was not entirely displeased, and as it was Shino who found them when he went to wake Itachi in the morning, he was discreet enough not to mention it.

The rest of the mission passed without much incident, although Satsuki was a bit more moody than usual and snapped at Kiba a few times. And she did eat most of the chocolate although she shared some with the rest of them. When Itachi mentioned this to his mother, she just gave him a placid smile and mentioned that it would have been much worse without the chocolate.

Sasuke endured not only the talk about the menstrual cycle, but also the talk about sex, which he really did not want to hear. He had no desire to let any male sexual organs anywhere near his person, thank you very much, and why did people keep forgetting he was only twelve? But at least it was out of the way and hopefully would not have to ever be repeated ever again.

"Hey, it's the cheater," An unpleasant voice said. Sasuke turned around; a plastic bag lightly dangling in one hand. It contained a paper bag of dango from a nearby sweetshop. Itachi was writing up a mission report, and Sasuke wanted to bring him something to eat. Standing behind him were Fuki, Kasumi, Masaki, and several other recent graduates from the Academy, all wearing their shiny new forehead protectors. With twelve members of his class graduating early, their teachers had probably focused their attention on the remainder so they had all managed to pass. Of course, he could take any of them one on one without breaking a sweat, probably even two or three of them, but there were seven… eight… nine of them.

His team had been dismissed for the day, Teams Ten and Seven were out on a joint C-rank mission to clean out some bandits attacking merchants and traders traveling to Hoshigakure, Team Nine was visiting Kusagakure, and Team Gai was still training (or at least Lee and Gai were).

"What's the matter, Satsuki?" Another voice taunted. "Are you too good to talk to us, now?" It was Odeki, a round-faced, pimply boy.

"She should be ashamed to talk to us, Odeki," Bitou, a skinny, white haired boy sniggered. "I heard she was spreading her legs to get information on her last mission."

That prompted a round of laughter from all parties. Sasuke kept his face emotionless. He was about to just body flicker away when a thrown kunai missed his hand and sliced through the bag of dango he was holding, causing it to drop to the floor. Dango spilled everywhere, some of it being deliberately crushed underfoot as they advanced on him.

Logically, Sasuke knew he should just ignore them, return to the shop later, and pick up some more dango for Itachi, after he cooled down a little. The analytical part of his mind noticed that the nearest security cameras had clearly picked up that they had thrown the first insults as well as the first kunai. The majority of his mind was wondering how smug they'd be after he called up Susanoo and put a few of Indra's arrows through them. Or perhaps maybe he should burn them slowly with Amaterasu or slowly torture them with Tsukuyomi? Fortunately, the paranoid part of Sasuke, which was always the loudest, protested vehemently that revealing the Mangekyo Sharingan was a bad idea and the Rinnegan would be an even worse idea.

So, Sasuke let them surround him, continue insulting him, and then, when they were about to actually inflict bodily harm on him, body flickered away to the Hokage's Tower to report a possible leak of sensitive mission information and sexual harassment. Then he went back to the sweet shop and bought more dango… and a tomato juice, to reward him for a job well done.

Weeks later, the Konoha Twelve and Team Gai were gathered near the Konoha main gate to welcome in the foreign Genin who were applying for the Chuunin Exams. Sasuke was keeping his eyes peeled for one particular team. He knew Itachi had given the Hokage the information on Orochimaru and the Akatsuki, but just in case, he wanted to be extra careful. Even the slight cramps he had didn't manage to distract him as he spotted a distinctive head of red hair. There he was…

Gaara was fairly used to being stared at. It was because he was powerful that he was feared. Shukaku and he both knew it was right to be looked upon so. But that girl with the shoulder-length black hair… there was something different about the way she was looking at him… and her eyes… she had eyes like his…

"You," He said, walking up to her, ignoring the gasps from his siblings and the people around her. "What's your name?" She smelled like blood. He liked it.

"Uchiha Satsuki." She said. "I've heard of you. You must be Gaara."

Inside his head, Shukaku rumbled approvingly. She's very powerful. She will be a good Mate for you.

"Uchiha Satsuki," Gaara looked her straight in the eye. "Date me."

End Chapter

Started 2/17/16

Completed 2/29/16

Most of the first two pages of this chapter were written before the rest of the fic was laid out, so if the writing style is different, that is why.

I bet Sasuke didn't see that coming!