A/N: I wrote this for myself, but I'm sharing it with you all. This is a soft-AU, so things might be slightly different than in canon. Anyway, I hope you enjoy it.
There was a flaw in the seal holding back the Kyūbi no Kitsune. It wasn't a symptomatic flaw, nor was it a flaw in the symbols that made up the seal. Thus, it was not a flaw that could have been spotted before it became apparent. And yet, it was the reason the Hyūga nurse had hurriedly excused herself from the room, leaving one four-month pregnant Kushina Uzumaki confused and very worried.
When the nurse returned a good fifteen minutes later, she wasn't alone. Three other men followed her in: Sato-sensei, her OB/GYN; Kimura-sensei, the hospital's chakra specialist; and, most alarmingly, her pale-as-a-ghost husband. Kushina, being the bright woman she was, connected the dots instantly, and the resulting picture hit her like a rasengan to the stomach. She stood. "No..."
Kimura-sensei raised his hands and motioned for her to calm down. "Now, now, Kushina-sama, Hyūga-san spotted something during your checkup and wanted me to confirm her observations. If you would please take of your shirt?" When she did, he held out his hand a few inches in front of her abdomen. At the same time, the pale-eyed nurse activated her bloodline again. "Now, would you channel chakra to your feet, as if you were performing the tree-walking exercise? Just a small amount will do," the chakra specialist requested.
Kushina's hands instinctively came together to form the ram seal. Less than a second later, Kimura ordered her to stop. "It's as we feared. Kushina, as of this moment, I am ordering you to never draw upon your chakra again until your baby is born. The seal on your abdomen is leaking the kyūbi's chakra into your uterus whenever you draw upon your own, and it has already... had an effect on your child."
The fourth hokage, upon hearing that, looked away from his wife and towards the chakra specialist. "What sort of effects?" he pleaded.
Sato put his hand on Kimura's shoulder. "Allow me, Kimura-san." The OB/GYN stepped up, while the chakra specialist ducked back a few steps. "As you know, I am also a chakra sensor, and between what Kimura-san, Hyūga-san, and I have all observed so far, I have a theory.
"You've probably felt that whenever you achieve orgasm, your body releases a large amount of chakra, yes? Every fertile human, man or woman, civilian or ninja, will release up to thirty percent of their chakra upon orgasm, unless they otherwise hold it back. This chakra is critical to the development of the fetus. When the father's sperm, saturated in his chakra, fuses with the mother's egg, saturated in hers, it forms the child's chakra for the very first time, as well as the 'seed' from which the child's soul will grow," Sato explained.
"And when Minato got me pregnant..." a rapidly paling Kushina realized.
"Yes. The seal of the kyūbi leaks chakra into your seventh abdominal tenketsu, the one used almost exclusively for feeding a fetus chakra, instead of your nearby fifth abdominal tenketsu," the OB/GYN confirmed.
Here, the chakra specialist added, "And with how dense and potent the kyūbi's chakra is, it almost certainly displaced the chakra on Minato-sama's sperm. In other words, while Minato is the father of your child's body, your child's soul was fathered by the Kyūbi no Kitsune."
"What do you mean-" Minato exclaimed. Kushina had opened her mouth, ready to shout even louder than her husband, but a strong pull from her gut silenced her. Her eyes rolled back in her skull, and she passed out.
A second later, Kushina Uzumaki woke to the sight of the Kyūbi, staked down onto the stone disk of the seal as usual. However, instead of his normal expression of pained rage, he bore a goofy-grin. And then he, of all things, giggled.
"Kurama."
Kushina blinked. That single word, combined with his expression, momentarily defused her rage. "What?"
"Kurama. My name is Kurama. You are the mother of my child. It is only fair I tell you my name."
"Your child? My child is nothing of yours!" Kushina screamed.
"Believe what you want, Kushina-baka," Kurama replied dismissively. "Your son is my son as well; my power courses through his veins, as I now see. And because of that, I'm changing the terms of our deal."
"What are you doing, Kyūbi?" Kushina demanded.
"My name is Kurama. I'm only helping you. From now on, as long as it's in the defense of our son, you may freely use as much of my chakra as you wish. Additionally, I will give you access to my emotion-sensing ability, and up my efforts to heal you whenever you are injured. In return, I expect you to love our child with all your heart, defend him, and help him grow up strong enough to be worthy of being my heir." Suddenly, the bijū giggled again, a noise that had no right coming out of the behemoth fox's mouth. "My heir. Oh, father, I must look like you did when Indra and Asura were born. Now I know how you felt. Hah!"
Lost in his own thoughts, Kurama barely even noticed the strained, confused expression on Kushina's face. For the first time in Kushina's and Mito Uzumaki's combined lifetimes, he was showing a side of himself that he had never shown either of his former jinchūriki before. And for the first time, Kushina found herself feeling the tailed-beast's chakra without the malice it normally held; it was still toxic and aggressive feeling, but playful and bubbly as well. "What has gotten into you?" Kushina asked, flabbergasted.
"The question is, what has gotten into you? The answer: my son! Hah hah! Never let it be said that foxes, even demon ones, make bad fathers."
Kushina, having nothing more to say to the fox, and now suddenly free from its pull, climbed out of the seal and back into the waking world, where a very concerned Minato Namikaze stood above her. "Minato?"
"Kushina! Are you alright?"
"Yeah, I..." A though struck the red-haired woman. "Minato, do you remember when I first told you that I was pregnant?"
He blinked. "Um, yes. Kushina, I don't think this is the time. What just happened? Was it the Kyūbi?"
"No, Minato, I'm serious. Just humor me with this: I need you to try to make that goofy smile again."
"Uhh... sure?" Despite the hesitance of his reply, he immediately cast himself back into his memories, trying to recall the exact feeling. A second later, a good replica of that smile appeared on his face.
Upon seeing it, Kushina groaned. "Damn. There's no way he was faking that."
"Who?"
"Kurama. The kyūbi."
Over the next four and a half months, Kurama regularly pulled Kushina into the seal. At first, it was only for a few minutes at a time, but it steadily grew longer and longer, the more Kushina and Kurama got to know each other. By the first month, they were telling jokes, and by the second, Kushina would count Kurama as one of her best friends and precious people, third only to her husband and Mikoto Uchiha.
At first, their conversations were strictly about the now named Naruto Ōtsutsuki-Namikaze, named after Kurama and his father and Naruto's grandfather, Hagoromo Ōtsutsuki, the Sage of Six Paths (though the baby would publicly be known only as Naruto Namikaze). Then those conversations grew to encompass history and techniques that Kurama wanted to pass onto Naruto, and then to techniques Kushina could use to defend her son with. Eventually, the two felt comfortable discussing anything under the sun, which was how Kushina discovered that Kurama could tell jokes so bawdy that they could overcome her own anti-pervert sensibilities and, upon retelling, make the great Jiraiya blush redder than Kushina's hair.
But, on occasion, Kurama would drop bombshells on the happy family, often without meaning to. For instance, while discussing potential training regimens, Kurama said, "I think he'll be able to handle more than that. After all, he is a demon."
"Kurama? What do you mean, 'he is a demon?'"
"Exactly that," the bijū replied matter-of-factly. "His soul was formed with demon chakra. Ergo, he is a demon."
"But Minato and I are humans! Wouldn't he be only a quarter demon?" Kushina inquired.
"No. You're either a demon, or you aren't. If you have even the tiniest bit of demon chakra, you are a demon. A weak one, perhaps, but a demon. And anything can be a demon, even spirits, like kitsune, and gods, like the shinigami, can also be demons."
"And what does that mean for Naruto?" Kushina asked, quite worried. She'd heard horror stories about demons, some of them from Kurama himself. Be it the demons themselves, or the humans around them, someone always seemed to suffer when they clashed. If Naruto was a demon, would the village demand her son's death? Would he be sealed away? On the other hand, would Naruto live a normal life until something happened and someone got hurt because of him? Kushina didn't know, and maternal worry filled her being.
The supernaturally empathetic kitsune frowned. "I don't know. Until his powers start to manifest, there's no telling what he will be able to do, or if he will even remain human-like in appearance."
The day of Naruto's birth was a mixed one. The masked man attacked and captured the newborn Naruto, and then unsealed and hypnotized Kurama into attacking Konohagakure. After taking his son and wife to safety, the fourth hokage fought off the masked man, while the subverted bijū rampaged. However, after Minato landed a good hit against the masked man and placed the contract seal on him, the man's connection to Kurama snapped, and the bijū froze in place. Then the masked man fled.
Kurama, upon realizing that he was free both of the seal and the mind jutsu, closed his eyes and leapt back towards the forests that surrounded the village. There, he sat on his haunches and bellowed, "NAMIKAZE! UZUMAKI! WHERE IS MY SON?"
From all the way at the safe house, Minato heard the beast's call. In an instant, he flashed alone to the closest hiraishin marker, then body-flickered the rest of the way to the waiting bijū. As soon as he arrived, Minato shouted, "They are safe, Kurama-san."
Kurama nodded. "Thank you, Minato-sama. And thank you for freeing me from that Uchiha's control. Having one's will subverted by the sharingan is a horrid experience." Being as close to the edge of the village as they were, having had some time since he stopped moving, and with how loud Kurama's speaking voice was, Minato was hardly the only ninja within earshot. Add in the fact that lip-reading was a basic ninja skill, and Kurama's words were hardly secret to any ninja in the village. Then, as if realizing that fact, Kurama vanished in a puff of chakra smoke, which then rushed inwards to fill a sudden vacuum. When it cleared, there stood a man that could have been mistaken for an Uzumaki, were it not for his orange hair or the nine orange tails twirling behind him. "Now, Minato-sama, we have something really important to talk about. But first, I would like to hold my son, and I think you would too."
Minato nodded, both agreeing with the literal intent of Kurama's words and the hidden message of "let's speak in private." With a flash, the two vanished, leaving behind several confused ninja.
Appearing back at the safe house, they arrived just in time to see Kushina stumbling out of the front door. "Kushina!" both men exclaimed.
"Minato!" She blinked. "Kurama?" The transformed bijū nodded. "What happened?"
The two men helped her inside and laid her back down on the bed next to Naruto, who was sleeping soundly. Using the sleeve of his hokage robes, Minato wiped the blood off of Kushina's lipps, blood that she'd coughed up during the unsealing.
"Minato-sama," Kurama said once Kushina was resting. "I want to be as far away from this accursed village as I can. Twice now, the Uchiha have subverted my mind, and my intuition tells me that it may happen again. I can feel a mokuton user in the village, and it was your first hokage's mokuton that captured my brothers and sisters. Were it not for the fact that doing so would deprive you, Kushina, and Naruto a home, and thus harm Naruto, I would gladly destroy this village and devour everyone in it."
Minato flared his chakra and grabbed a hiraishin kunai.
"Make no mistake," Kurama continued without even batting an eye, "I am the enemy of this village, but you hold something of far greater value to me, and that is why I do not attack. Were it not for Naruto, I would still despise Kushina for torturing me every single moment I was inside her, but as it is, I hold no grudge against her. Or you, for that matter. You have done me no wrong, and have done me several favors, Minato-sama. I owe you, which is why I offer you this choice: I will take Naruto with me, away from this place, and train him as my heir. You can either come with me, or visit whenever you like. Alternatively, Kushina can seal me away inside of Naruto, so that I may protect him from the inside."
Minato, being the loyal leaf ninja that he was, didn't even consider the first option. So he asked, "Why Kushina? Why not me?"
Kurama. "Because... I smell death on her. Her chakra is failing. Without help, I doubt she would live a week. With it, maybe she'll survive, but if she does, she'll be without her chakra for the rest of her life. It will be a short, miserable experience. Sacrifice yourself if you want, but know what you're leaving behind."
The moment Minato figured that the village situation was stable enough that he could take a small break (mentally justifying it by the fact that he was leaving a shadow clone behind), Minato flashed back to the safe house. There, he finally was allowed a good, long look at his son. On top of Naruto's head was short, golden blond hair that reminded the fourth so much of himself. On his face, three dark, jagged, whisker-like markings dotted each cheek. His little hand, which was poking out from under the blankets, had fingers tipped in little claws.
Minato mentally scaled up both of those features, trying to visualize the baby as an adult. He looked at his own hand, felt his own face, and realized that those features, while adorable now, would look quite savage on an adult.
Naruto stirred. And then, for the first time in his short little life, he opened his eyes. His three parents gasped, but none gasped louder than Kurama, who swooped in and put his face right in front of Naruto's. The little boy looked back up with unfocused, solid purple eyes. Save for the tiny, circular pupils in the center, his eyes were one solid hue with no boundary between purple iris and equally purple sclera. "Kurama?" the exhausted Kushina asked.
"It's the rinnegan! Or, at least, a defective, incomplete version of it," the fox explained.
"Incomplete?"
"Yes. It's missing the concentric rings. What this means for Naruto, I have no idea. Perhaps he can do everything my father could; perhaps he can do none of it. Only time will tell."
As Kurama had predicted, Kushina succumbed to the combined stress of childbirth and bijū extraction and died only two nights later. Kurama watched the funeral from a distance, and though the world saw him as stoic, he mourned silently.
In the end, Hiruzen Sarutobi was the one to finally seal Kurama away. The kitsune was getting antsy, and with one of Naruto's parents deceased, there was very little stopping him from taking Naruto and running. Yet, when the former hokage came to seal the kyūbi, he went without complaint.
The reaper claimed Hiruzen's life a moment later.
In the end, there was mourning, and then there was unease. Not many had died in the initial attack, but the lingering chakra of the kyūbi caused almost every civilian pregnancy, and a sizable number of kunoichi pregnancies to miscarry. Kurama's own words meant that much of that anger was directed at the Uchiha clan. That Uchiha children were also lost was lost on most people, who now refused to meet the eyes of any Uchiha at all, sharingan or otherwise.
As for the now ostracized clan, their grieving families turned to the rest of them and demanded answers. Under the assumption that there was a traitor among them who had orchestrated an attack on their own home, their own heirs, the clan turned its gaze upon itself, and did not like what they found. Though the primary culprit, a man by the name of Madara Uchiha, was not found, several others guilty of comparatively minor crimes were found. They were executed a week later.
As the village recovered, which ended up being a fairly swift process, rumors started cropping up. The kyūbi was apparently intelligent, and was willing to allow itself to be resealed for the sake of its son, so who was his son? That he was intelligent, and that the fourth claimed a degree of friendly acquaintanceship with the fox also had people speculating. Who was he? What were his intentions? The fact that he was a father who had, the moment he was free from hypnosis, asked for his son, garnered him some sympathy among the denizens of Konoha.
When people talked, spies listened. As it just so happened, one of those spies was from Kumo. When that spy eventually sent his report, the raikage's brother, Killer B, was in the room when A received it Upon hearing the report, a two-tailed chakra cloak materialized around the jinchūriki.
"Killer B?" the surprised raikage asked.
"Oh come now, this ain't me, bro. Gyūki says we have to go!" Killer B rapped, though his voice was questioning in tone. Then, with no further warning, the eight-tailed jinchūriki bolted out of the room with bijū enhanced speed.
The raikage facepalmed.
One of his ANBU materialized next to him. "Raikage-sama?" The raikage made a noncommittal grunt and just waved his hand. He knew Killer B wouldn't get into trouble, and figured that this was just one of those things that he had to let slide.
Probably.
Maybe.
On second thought... "Follow him. Make sure he doesn't screw up anything too badly. And also, when he does cause trouble, make sure that the people in his path know that he's doing it of his own will, and is not acting on orders from Kumo."
"Yes."