Disclaimer: If I owned this, I would be awesome. But I don't, so therefore I'm not.
AN: I've come up with yet another idea, this one a Naruto/Soul Eater crossover. I've seen a couple fics where Naruto gets the Black Blood like what Chrona has, but they are all unfinished and most weren't well written. My plan for it is somewhat unique. You remember how they said that the Third Raikage had 'a body like steel and blood like iron' that gave him his insane durability? Well, what if that was the result of a rare bloodline that appears only once a decade in random people called the Black Blood release that gives the user inhuman durability on par with the Kaguya Clan?
Naruto, as it turns out, was born with this bloodline. However, when Kurama was sealed into him, his chakra had an interesting effect on the Black Blood: it became sentient. It eventually awakened as its own personality (Ragnarok) that becomes fully aware when Naruto is 5. Thanks to Ragnarok's sentience, Naruto can use the Black Blood in ways that were previously unheard of (Bloody Needle, Blood Sword, Blood Dragon, etc). Later, Ragnarok also figures out how to use chakra to manipulate sound waves (Scream Resonance) like Dosu of the Sound Ninja.
Mostly Ragnarok will be in his smaller chibi form, but when Naruto uses the Kyuubi chakra he'll become his more adult form and can use certain attacks like becoming a dragon. This will also have the added benefit of giving Naruto a very unorthodox friend.
Naruto of the Black Blood
A five year old Naruto Uzumaki got up with a groan from the snow he lay in. He had just went to rescue that cute (if somewhat weird) pale eyed girl from that group of bullies (1). However, instead of pulling off a big dramatic rescue that made him look super cool and epic for all to see, the blonde whiskered child had gotten on the wrong end of a beat-down when his attempts at performing the Clone Jutsu bombed spectacularly. Now it was getting near dark, his scarf was laying in tatters around him, his head throbbed from the multiple kicks and punches it received, and his black blood was dripping out his nose from a particularly hard punch to the face. Oh, did I forget to mention that Naruto's blood is black?
It was the day after Naruto was born that the Third Hokage had made the discovery when he took Naruto to be examined by the medic-nin to make sure he was born healthy (you know, besides that whole 'giant fox in the gut' thing). When the doctors had went to take a blood sample, they were shocked to find that, after needing to use more force than normal to break the infant's skin with the needle, that the boy's blood was black in color! This was the result of a very rare bloodline that only appears every so often. Unlike other bloodlines, it is not passed from parent to child, but instead is caused by a rare mutation in the host's genes. Only a handful of people have been recorded to have this trait, the most famous example being the Third Raikage. What this bloodline does, besides giving the blood its odd pigmentation, is increase a human being's durability nearly a hundred fold. It makes it nearly impossible for the user to be deeply cut by a blade, and while physical blows can hurt (as evidence by Naruto's mild concussion), the damage done is not nearly as severe as it can be to a normal person. It was part of what made the Third Raikage such an indestructible tank on the battlefield, the other reason is that he trained his body to the peak of physical fitness to increase his already durable body to the level where he could fight the Eight Tails to a standstill.
Naruto, when he was old enough to understand this, was predictably excited about this, thinking his already super awesomeness was bound to increase dramatically thanks to having his super rare bloodline. Though a part of him did wonder if it was because of his different blood was why people seemed so cold towards him, the Third assured the boy that this wasn't the case. So for now, Naruto accepted that he was special in his own way, and that it would help him further his dream to becoming Hokage. Little did he know how right he was…
Something unique was happening inside the boy as he sat there in the snow, something that had been set in motion the moment the Nine Tailed Fox was sealed in him as a baby. The Black Blood, being so rare, had never been present in someone who had a Tailed Beast sealed within them. The results, if observed, where quite shocking. The corrosive chakra mixed with the Black Blood, fusing with it, and actually causing a spark of life to form within the black fluid. Over the years, this life continued to grow and mature within the unknowing boy. The being that formed began to learn of the world around it as it pulsed through Naruto's veins, learning of words, people, places, things, and ideas. This new life had been waiting, watching, for the moment it gained the strength to become fully self-aware. That moment was now.
"That was pathetic!" an echoy voice seemed to say to Naruto, though the clearing was empty save for himself.
Naruto jumped and looked around, trying to see where the (creepy!) voice came from. "W-who said that?" he stuttered.
"Me, you idiot, who else? Are you seriously that dumb or are you just trying to play on the blonde stereotype?" the voice said tauntingly.
Naruto growled at that, shock momentarily forgotten. If there was one thing he couldn't stand, it was being made fun of. "Listen you jerk, knock it off and come out where I can see you or I'm gonna kick your ass!" the jinchuriki shouted out.
"Ohh~! So scary blondie! Aw, what the heck, it's no fun ruffling your feathers if you can't see me. Hold on a sec," the voice then paused before Naruto felt an odd sensation on his back.
It almost felt like when he put his hand on the tube of a vacuum, a weird, sucking feeling. It wasn't really painful, but it was definitely odd. What Naruto didn't see was that out of his back, his Black Blood was seeping out of his pours like sweat but in much greater quantities. The blood then began to flow and twist, taking on a shape as it partially lifted itself from his back. The liquid took on a solid like quality, becoming a completely new shape as the being that was given life through Tailed Beast Chakra and Black Blood was formed. The being's body was small but muscular, with round gloved hands, and spikes on several parts of his body, but no legs as its lower body was protruding from Naruto's back. His face consists of a large egg shape, with no visible mouth and a giant white X on his face where his nose should be, with large ping-pong ball-like eyes with X's for pupils. The being leaned over Naruto's head until its face was hanging upside down mere inches from the boy's nose. A large, toothy smile formed on the seemingly blank face and the voice from before said, "'Sup?"
Somewhere in the Hidden Rain Village
A figure with ring patterned purple eyes raised his head at the piercing scream that tore across the area. He mused, "Hmm, someone has learnt the true meaning of Pain."
He then went back to look over the details of the decade long plan in the making.
Back with Naruto
Naruto desperately tried to back away from the black…blob…person…thing. However, this was made pointless due to the fact it was coming right out of his back. "Who…what…how?!" Naruto babbled incomprehensibly for a moment before the blood creature brought a fist sharply down on his skull, causing him to yelp in pain. Small or no, the thing had a punch like iron!
"Calm down blondie! Jeeze, if I had ears I think I'd be deaf after that. Anyway, nice tah finally meet yah! Names Ragnarok," the now identified Ragnarok said.
"R-Ragnarok?" Naruto questioned numbly, still trying to comprehend the creature coming out of his back! It was then he remembered where he heard that word before. A few weeks ago, a traveling storyteller had come to the Leaf Village and was telling his tales in the village center. Naruto, like most children, got interested in hearing tales of lands far away. One of the stories the man spoke of was a people far to the west who believed a great battle would occur at the end of time, a time they called Ragnarok (2).
"Yep! Liked the sound of it when that guy was talkin' about all that 'end of the world' crap, so I figured I'd name myself that. Got a problem with that?" Ragnarok questioned while his eyes seemed to narrow at the wielder of the Black Blood.
Naruto quickly shook his head in the negative, not wanting to upset this strange creature. "N-no! It's a very cool name!" he then took a breath to calm his nerves, scrutinizing Ragnarok carefully. "Anyway…" he started slowly, "What are you anyway?"
Ragnarok's bulblike eyes seemed to crinkle in a grin as he replied, "Well I'm made from your blood, duh!"
"My blood?" Naruto asked with a huge question mark over his head as he continued, "How's that work out? The Old Man never mentioned anything like this when he told me why my blood is different! And how are you able to talk and think and stuff? Aren't you supposed to be in my body if you're really my blood?"
Ragnarok shrugged his shoulders in a nonchalant manner. "How the crap am I supposed to know that, dumbass? I just really woke up a couple days ago and could actually form outside your body today. Basically, I know everything you know. I'm just better at it then you are," he finished smugly.
A tick mark appeared on Naruto's head. "Hey, watch it! I'm gonna be the future Hokage, ya know? So show a little respect! 'Sides, you're living in my body right, so doesn't that mean I'm your landlord or something?" he asked hotly.
Ragnarok rolled his eyes before bonking the blond on the head again. "Wrong whisker face, if anything you owe me for keeping your sorry hide alive. As for the whole 'being Hokage' thing, how are you gonna pull that off when you get the snot kicked outta you by a bunch of toddlers?" he chided.
Naruto rubbed his abuse skull while grumbling for a moment before glaring back at the Black Blood being. "Shut up! I'm gonna get better, believe it! Then I'm going to be the best Hokage the village has ever had!"
The two stared at each other for what felt like an eternity before Ragnarok started chuckling which soon developed into full blown laughter. Naruto angrily demanded to know what was so funny, but was ignored until the living blood finally quieted down, wiping an imaginary tear from his eye before turning back to the boy with a big grin developing on his face. "Heh, I like that attitude kid! Let's see how far that determination will take you. I'll even lend you my strength just to see if you can prove me wrong!"
Naruto looked to him in confusion. "Huh? What can you do? And why would you wanna help me anyway, I thought you figured I was pathetic?"
"Oh trust me, you are pathetic," Ragnarok said while waving a hand dismissively, continuing despite the new glare he was receiving. "But it would be pretty boring just lazing around in your sorry self while watching you get kicked around like earlier, so I'll help you out for the entertainment value. Plus, if you're holding me then you're representing me, and I don't feel like having a pussy for a wielder. As for what I can do, didn't I just say I was made of your blood? Give your finger a small cut and you'll see what I mean."
Cautiously, Naruto brought a finger to his finger and gave it a nip with his canines. Looking at the now slowly bleeding finger, Naruto wondered what was supposed to happen now.
"Bloody Needle," Ragnarok called from Naruto's back, and suddenly with an odd feeling running all the way through his body, the blood seemed to burst out of the pinprick on his finger before solidifying, becoming a long sharp needle poking out of Naruto's finger.
"Whoa!" Naruto cried out in shock while falling over again, watching in awe at the clearly deadly weapon forming from his very life fluids before it dissolved once again into liquid form, splattering into the snow on the ground. With wide eyes, Naruto looked back to Ragnarok in hopes for an explanation.
Ragnarok seemed to smirk before elaborating, "Told you, I'm made up of your blood so I can control it as I, and now you, wish. Plus, since Black Blood is stronger than normal blood, it can form weapons way easier! Trust me kid, with me around you can become one of the most badass ninja on the planet! So what do you say, partner?" he finished while holding out a hand expectantly.
Naruto quickly weighed his options. On the one hand, Ragnarok came across as rude, sarcastic, violent, and more than a bit creepy. On the other hand, Ragnarok was staying with him no matter what thanks to him literally being a part of the boy, the skills he could gain from Ragnarok had endless possibilities, he was right in that the blond was currently lacking in the skill department, and maybe, just maybe, he wouldn't be so lonely all the time anymore.
Throwing caution to the wind, Naruto reached out and bumped fists with Ragnarok. "Deal, partner," Naruto replied with a big grin forming on his whiskered face.
1. This scene is from the movie, Naruto: The Last.
2. I'm not overly familiar with Norse mythology, so sue me if my details are off. Also, I figured a story teller from a land far to the west would be the best method of finding a name for Ragnarok instead of him just pulling it out of his ass.