40 years before the second great Shinobi World War:The Reikon Yaiba clan was originally a group 3 of fanatical swordsman who wanted the ability to imbue their swords with the souls of strong deceased shinobi with hopes to increase the swords destructive ability. They attempted to put human souls into swords for almost 20 years before they were able to. To do so they contracted a talented man to guide the dead souls into the swords and then seal them in once they entered.
It worked, and the ability of the swords was increased tenfold. Not only did the dead persons elemental affinity follow them to the grave, it was engraved in the sword once they were sealed in. The sword having a soul also allowed the sword to grow with the swordsman, making it fit the sword owners abilities and needs.
Eventually they came to strong disagreements on what would be allowed in the clan. The most fanatical member of the beginning 3 revolted and killed the other two, and put their souls into his blades. After all, although he defeated them they were incredibly strong shinobi, and would make a great tandem with their 2 chakra affinities of Fire and Wind. The man who would become the first leader of the clan, Tokiji Jakazi took power and promised to make the clan powerful.
The clan grew and grew until it reached to over 100 members spread across three hidden villages (Mist, Rain, and Sand). The clan remained in the shadows due to the fact that putting unwilling souls into swords was strongly frowned upon by the government in all hidden villages. They managed to remain under the eyes of the government for a long while, but eventually they were ratted out by a former member who was expelled from the clan due to his insanity.
The Reikon Yaiba clan then become a rogue clan of swordsman for hire. They continued their practices, but were even more discreet about them than before, and only performed such soul sealings for their closest family members. The clan was now in chaos though, and the leader had no more power to lead the clan into the light. Their numbers decreased and decreased as they were hunted down as missing nin until the leader of the clan, Tokiji Mayato agreed that the clan would only use souls of deceased clan members in their swords. Some of the member returned to their hidden villages, others decided to take an opposing route.
This however caused a civil war within the clan. The two opposing parties were called the Kinnouka and the Kyuushin. The Kinnouka did not want to change the clans customs and intended to keep forcibly sealing souls of the dead into their swords. Going so far as to track down strong shinobi just to take their souls unwillingly after death. The Kyuushin believed in radical change and wanted to be able to return to their villages and have peaceful lives without being hunted down by the government and bounty hunters. This would eventually tear the clans reputation into the ground. People knew the difference between the Kinnouka and Kyuushin, but they always connected the two in their minds whenever the thought came up. Now forced into the open, the Kyuushin were looked down upon as one of the most corrupt clans in the shinobi world, and were hard pressed to find good jobs.
In the present day, the Kyuushin and Kinnouka are still at war. While the Kinnouka has decreased in population and the Kinnouka has increased, the most powerful members of the clan still reside in the Kinnouka and are gaining power much faster than the Kyuushin.
Clan's Secret Techniques or Bloodline traits:
Bloodline: Hane Yaiba (Feather Blade): All members born into the Yaiba clan possess and innate ability to handle swords. The weight of the sword does not effect members who inherit the bloodline. The weight of each sword is decreased between 25% and 75% of the actual weight while in the hand of a bloodline member, and this bloodline has no know negative effects. The percentage of weight it decreases is based on how strongly you inherit the bloodline. This effect is automatic as well, and can not be changed in any way shape or form with training or age. However, the weight remains the same in members who do not have this bloodline, and makes the swords of strong members of the clan nearly impossible to wield by anyone else.
Bloodline: Eye of Mayato [very rare, only descents of the nobles can finally obtain these eyes.]: This is inherited by direct descendants of Mayato. The eye allows you to see through a persons true intentions, and see through lies. This effect is 100% fool proof, unless someone has an ability to counteract it.
Sword Affinities: Every sword in the clan possesses the strongest affinity of the soul of which died. This is the strongest element of the Reikon Yaiba clan, and what they are mainly known for. For example, if the soul that died was a Fire element user, then the sword would be able to light on fire without using any hand seals or chakra from the swordsman. The abilities of the sword and its affinity are wide ranged and different depending on each sword and its power.
Chakra Transfer: When the Soul is transferred into the blade it regains 10% of the chakra it had before it died. This Chakra is mainly used for the Sword affinity stated above, but it can also be used to heal the swordsman in dire situations where death is imminent. The sword running out of chakra does not effect it other than keeping it from using abilities that are chakra related. Basically it is reverted to a standard sword.
Evolving Blade: The Swords of the Reikon Yaiba clan evolve and grow up with the user. The sword has a preset amount of potential it can reach based on the power of the person that the soul was in before it died, but it is able to increasingly unlock that potential as the owner of the sword increases their strength. For example, an academy students sword could very easily be the size of a small knife, while a sennin's sword could reach the size of an adult male. Size is not automatically equal to the swords ability, but it is uually a good measure for the swords ability.
Soul Connection: From the instant when a member of the clan receives ownership of his sword through a ritual, their souls are intertwined. They can hear each others thoughts and feelings. They are able to tell each other things in battle, and that often leads to a strategic advantage. This also makes it so the sword will render itself useless to someone who attempts to wield it who is not the owner. They can deny a false owner in many ways, one way is to completely stop using chakra and make it's blade dull, another way is for the sword to use its elemental affinity to hurt the false owner. This however is not the case for the Kinnouka. Since the souls they put in their blades are not willfully there, the swords will often attempt to rebel against their owner, which can cause the death of the owner if not powerful enough to handle it.
Reikon Yaiba Sword Style: The Reikon Yaiba style is based on strong, and fast multiple strikes intended to decapitate the enemy. This style is extremely aggressive and is intended to keep the opponent on the defensive and not give them time to go on offense.
Tokaji Mayato was a famous swordsman from the hidden village of grass. Few rivaled his ability to kill with the blade, and because of this he was known as one of the strongest shinobi in the world. He was often called the "Green Giant" because of his massive size, and his gigantic sword which was rumored to cut people in half vertically with barely any effort at all.
Mayato became annoyed with life in the village, and seeked to gain more and more power. He left the hidden grass village, but the village tried to hide this by saying that he was on an important mission so as to not tip off other nations that they were considerably weakened by his absence. During his travels he met 2 other incredibly strong swordsman names Hanzo Ko, and Ysube of the sand.
They all were looking for a way to gain power. They eventually turned to the thought of attaching souls to blades. They spent a good portion of their lives attempting to find a way to do this, and when they did find out, their power grew to inhuman magnitudes. The power went to their heads though, and when the thought to create a clan to increase their power in the shinobi world came up, they all wanted to be leader. Eventually they fought eachother for the rights, and they both fell to Tokaji Mayato.
Eventually Tokaji Mayato increased the clans size and made them a powerful figure in the shinobi world. Even he could not live forever. He died of old age 2 days after he reached the age of 67, passing on his legacy to his son Tokaji Jakazi.
He is worshiped as a deity by the clan, and his swords are placed inside a chakra protected glass case inside the main headquarters of the clan. Members frequently come to pray for guidance.
Seiji has now become one of the most powerful member of the Reikon Yaiba Clan and the only one left who has obtained the true powers of the bloodline trait, he had not a single clue who his family was as he was raised by an older woman of the clan who had been one of the great Sannin of the hidden mist village at the time. Her name was Kagerou of the flames. She obtained great power through all of her years of the Shinobi world because she had lived a long time in life, he actual age was 76 yet she looked like she was 40 due to her physical and youthful appearance. Kagerou had shown him the clan's skills and allowing him to master all thegreat powers of the clan's swordsmanship not only the basics she had shown him the ancient technique of the Hane Yaiba though only true members could learn this technique.
She lived on the outskirts of the Mist village so she allowed him to attend the Ninja academy in the village which allowed him to become very skilled ninja in his squad, though when he finally graduated from jonin and became a anbu black ops member he found out that Kagerou was once the villages great sannin but she retired from her old age. She wanted to teach him all about there clan's Kekki genkai so he can carry on there legacy, She and seiji agreed to finish his training which lead them to wander the world for three years picking up new techniques he could use into the future . When they had returned to the village he had mastered the true arts of the clan's sword style. Each sword has a life of its own and it chooses its wielder not the other way around like most people think. He had been given the sword from Kagerou who had kept for many years after her friend die tying to master this powerful sword, But even though its power was dark and impure she knew that Seiji could master it after all he had trained for this moment.
The sword had a very rare chakra element, it was a dark chakra type that was branded the name of Tatsou this sword would be a very difficult one to control because of the soul's power and chakra though the training with this sword would be very dangerous and could actually be at the cost of loosing his life, months of training blew by as Seiji managed to pull himself together and create an alliance with Tatsou . The sword eventually accepted Seiji and his story grew across the village. A small war had still waged between the mist and other villages over stupidity of politics, Kagerou's has grown ill at the last year of Seiji's training before they returned to the village. Though Seiji wanted to help with the war he decided he would tend on her as much as he could even though he knew it was only a matter of time. Finally came the day that would haunt Seiji for the rest of his life, he had been gone to fetch some medical herbs and medicine for Kagerou and among returning he came across two rouge ninja's paid by the Hidden grass village to assassinate a certain few hidden mist ninja on a list.
There stood two ninja looking down upon Kagerou's dead corpse with her throat slashed and a pond of blood surrounding her dead body, Rage coursed through his veins as a power he had not felt before overwhelmed his body and a burning sensation grew in his eyes. They high ranks called it the eye of mayato which must of meant that he was a child of one of the noble families in the clan, his eyes contained the power that allowed him to see through a persons true intentions, and see through lies. Now his wrath unleash massacring the two men instantly with body parts and limbs covering the room he walked over to Kagerou's death place. Reaching down and lifting her up he took her to there favorite places to go after a long days of training as he berried her with her sword right next to the partly blossomed tree that she always sat by. The sun had been setting and the breeze of wind felt very cold against him, only leaving to realize that he was alone. Finally after paying his respects to her grave leaving many years of memories he had only one new purpose in life. To embrace the this hate that has fueled his wrath and unleash it on the world, soon breaking all bonds with the village and friends that he may or may not have made, which he eventually ended up joining the Akatsuki.