Taikyokumaru

is an ancient sword in the possession of Shūhei Kaneyama. Once housed in a shrine atop a remote mountain in the far west, the blade was used as a vessel to away a pair of wicked entities. Due to the true nature of the sword, Taikyokumaru is known as one of the world's legitimately and ranks highly among them.

History
The origin of Taikyokumaru begins not with the blade itself, but instead with the tale of and, a pair of demons that terrorized the mountains regions in the western provinces. Centuries ago, minor settlements across the land were at the mercy of bands of bandits, and the occasional demon. Such demons, which have found their way into shinobi territory, often fed upon the the local inhabitants before retreating back into the mountains. Historically, some entities were even offered timely human sacrifices by villagers, hoping that they could appease the vile creatures and prevent random attacks on their homes. Takemaru was a wandering who traveled from between villages, consuming the the souls of unfortunate maidens he met along the way. Conversely, Kiyashahime was a who was offered the life of the strongest man in the region once a year by the villagers. Spiriting him away to her mountain abode, she would siphon away his vitality until his life was extinguished.

While their individual practices continued through several generations of humans, things dramatically changed when Takemaru and Kiyashahime crossed paths. At first a great battle ensued between the two demons, fighting over supremacy and control of the territory, which scorched the land itself. In the aftermath, neither demon had lost its life and a clear victor could not be found. As such, an unholy alliance was formed between the two demons. While usually solitary creatures, the pact forged between Takemaru and Kiyashahime resulted in a great calamity for the region. While the greed of a single demon is by no estimate small, the compounded desires of the two working together led them on a path towards conquering the region itself. Nearly immediately after joining forces the two great demons slaughtered the inhabitants of the villages around Kiyashahime's mountain to give birth to a demonic army unlike anything seen before.

Working her strange techniques Kiyashahime animated the corpses of the fallen villagers, who were then fed the blood of Takemaru and transformed into beings that resembled their parentage. These children, as the two demons referred to them, were tasked with the construction a demonic castle atop the mountain before beginning to spread their influence outwards. While numerous attempts to hunt down the calamitous duo were attempted by the strongest warriors around, all of them were met with destruction. Eventually, the expanding threat of the demons resulte in a alliance between the and  from the  setting off to eliminate the threat. Carving their way through the demonic forces of Takemaru and Kiyashahime, the group finally made their way to the castle. It was here that the band of humans faced their greatest challenge yet.

While the demonic creations boasted destructive abilities far beyond normal humans, Takemaru and Kiyashahime powers were on another level entirely. The duo decimated the samurai and onmyōji forces, crying out in anguish at the blood of their children that had been spilled by the invaders. After a long fought battle, the last surviving member of the samurai was able to impale Kiyashahime with his sword just as Takemaru ran him through. While this sacrificial move cost him his own life, the samurai had immobilized the demons just long enough for the leader of the Ashiya clan to seal the two oni with the Nine Syllables Sealing Method. While normally sealing evil entities into weapons was against the policy of the Ashiya, since such an item can become potentially more dangerous than the demon iteself, the samurai's blood-soaked blade was the only item of sufficient quality sufficient quality in the vicinity that could act as a vessel for the the demons.

With the battle finally over the castle, which had been set ablaze during the fight, began to finally collapse. The sword was taken by the surviving members of Ashiya and housed in a remote mountain shrine. This shrine was constructed for the purposes of keeping the blade away from war. More specifically, the the shrine was designed to keep the blade named Taikyokumaru away from the taste of blood, which would cause the demonic impulses Takemaru and Kiyashahime to stir once again.

Abilities
As a, Taikyokumaru possesses traits far beyond that of a normal blade. Beyond its arguable peerless edge and unnatural durability, the demonic spirits within the the blade imbue Taikyokumaru with additional attributes. Inheriting the hunger from the the demons Takemaru and Kiyashahime, the blade has the unique ability to siphon and absorb the spiritual and physical energies of individuals and entities. It is for this reason that the blade has earned the name.

Differing from direct, repeated exposure to this effect can temporarily reduce a victim's ability to form , which lowers the maximum magnitude of techniques they can perform. Additionally, extensive loss of spiritual and physical energy will cause an individual to demonstrate significant mental and bodily fatigue, respectively, without necessarily exerting themselves. In a heated fight, where one's stamina and focus are constantly pushed to the limits, shaving off an opponent's reserves can quickly push even the most stalwart of fighters into a corner. While most efficient with direct contact, the blade does possess the ability to siphon some amounts of energy from an opponent when colliding with a weapon used in melee combat.

In addition to this standard performance, wielders of this blade have demonstrated the ability to selectively target either an individual's physical or spiritual energy, rather than consuming both types of sustenance simultaneously. By doing so the absorption rate of the selected form of energy is significantly increased, allowing the user to coordinate their intent with much more precision and efficiency. Furthermore, such performances impart the target with more critical effects, but sacrifice the ability to reduce a victim's maximum chakra output.

When utilizing the purely spiritual variant, a lethal blow dealt by Taikyokumaru will completely extinguish a victim's soul, thus preventing them from being resurrected or revived through any conceivable means. This is due to the fact that such an attack causes the blade to assimilate and deconstruct the final portions of a victim's spiritual energy, destroying the soul and preventing it from entering the. It is for this same reason that the blade is especially useful against individuals summoned with, since Taikyokumaru will be able to deal direct damage against the bound soul.

In comparison when Taikyokumaru is commanded to absorb only a victim's physical energy, the blade can directly inhibit an individual's ability to heal themselves. While the effects are not permanent, wounds dealt by the blade in this form prevent the activation of regeneration abilities, such as   and even inherent. This property also applies to the, if the victim attempts to use it on themselves, but does not stop a third party from repairing the damage with the aforementioned technique. Also, should the victim of the blade bare old wounds Taikyokumaru's strikes can cause the victim's scars to rupture, dealing additional damage. This particular trait has been shown even when an opponent intercepts the blade with their own, which often leads to confusion on the victim's end.

Regardless of which variant the wielder is utilizing, this consumption ability cannot directly absorb chakra from an individual or techniques. Likewiese, the energies that it does consume are not passed onto the wielder. As such, the user of Taikyokumaru cannot directly benefit from the avarice of the blade. Despite this, once the blade has consumed a substantial amount of energy for the time being, the excess energy that it steals can be used to reinforce the spiritual and physical attacks used through the sword. More specifically, it can amplify the power of sword based and pure  strikes, respectively. Shūhei Kaneyama, the current wielder of the blade, has been shown to forcefully activate this ability by feeding demonic sword his own blood, but has admitted that it is a risky maneuver. He has also has mentioned that there is the the potential to tap into more of the demon's natural abilities, but that such traits are current inaccessible due to the nature of the two seals that bind the sword.

Finally, when the sword is released from it's first seal, as seen when the sword is drawn from its sheath, it demonstrates a vicious separate from the wielder's own thoughts and feelings. The strength of blade's will is strong enough for individuals in the vicinity to imagine the blade wrapped in a malignant aura, or even cause hallucinations where the blade's wielder takes the form of a vile demonic warrior. Notably, Shūhei has stated that wielding the blade unsheathed for extensive periods also has a negative effect of his mental state, in which he feels more inclined to follow the destructive will of the sword. This trait also makes the blade nearly unusable for amateur swordsmen, who would either be paralyzed by the will of blade or consumed by its desires.

Trivia

 * The sword's name can alternatively be written with the characters for, a philosophical term from which the concepts of Yin and Yang originate.
 * The demons Takemaru and Kiyashahime are references to the mythological characters and, respectively.