Kāma

Kāma is a seal that serves as a compressed backup of an Ōtsutsuki clan member's biological data that they can embed in the body of a compatible recipient known as a. Over time the Kāma will gradually overwrite the vessel's genetic profile until they transform into a perfect Ōtsutsuki. Should the Ōtsutsuki be slain their will migrate to one of their vessels, and when the Kāma completes will  through their body, completely replacing them.

In the interim, the vessel can learn to activate the Kāma and utilise a portion of the Ōtsutsuki's power and abilities, and if reincarnation has not yet been achieved, the slain Ōtsutsuki can even manifest and take control over their body.

Compatibility with an Ōtsutsuki is exceedingly rare and unpredictable, and if an individual is not a suitable recipient the ritual will typically result in them suffering a fatal seizure. Occasionally an unsuitable vessel will survive the ritual, however, producing a unique variant of the seal called the. Such individuals are unable to serve as a receptacle for the Ōtsutsuki's soul and thus cannot be used for the process of reincarnation, but retain its other traits, gaining tremendous power and even being able to transform into a completely new Ōtsutsuki.

Appearance
Though the Kāma superficially resembles a tattooed seal, it is actually a pyramid-shaped barb that is embedded in the vessel's body. Upon activation the visible marking will spread across the vessel's body, at times taking on different patterns depending on the abilities being used. Typically black, these markings may also shimmer and glow with a particular colour when activated, and when viewed up close appear to spread in patterns resembling microscopic circuitry. Kāma may produce a variety of different patterns depending on the individual, where on their body it is embedded, and what abilities are being accessed. As its name implies, the White Kāma is white in colour rather than black.

Isshiki Ōtsutsuki

 * Jigen: Isshiki embedded his Kāma into Jigen's chin while parasitically fused with his brain, after being betrayed and nearly killed by Kaguya Ōtsutsuki. When activated it spreads across his face and body in nearly symmetrical sunburst patterns. Progressing further, he sprouts a long horn identical to Isshiki's. This Kāma served its purpose and vanished when Isshiki was forced to reincarnate through Jigen's body.
 * Kawaki: Upon realising that Jigen's body would not be able to sustain his chakra, Isshiki transferred his Kāma into Kawaki's left palm through scientific experiments and a ritual conducted with the aid of Amado. When activated it spreads across the left side of his body forming a pattern that almost perfectly mirrors Boruto's, extending up to his left eye, and then glows red. Progressing further, he sprouts a short horn resembling Isshiki's. He lost this Kāma when Isshiki resurrected via Jigen's body, but later gained another one under unknown circumstances. Isshiki's Kāma in Kawaki was estimated to be 80% extracted prior to its removal.
 * Code: Among Isshiki's previous failed candidates was Code, the only failed vessel of the children Jigen gathered that survived the ritual. As such he bears a White Kāma, which is located on his left palm. As Code is not a vessel his Kāma did not vanish upon Isshiki's death, and before his soul expired, Isshiki entrusted Code with carrying on the Ōtsutsuki's will and bade him to become a complete Ōtsutsuki by sacrificing either Boruto or Kawaki to Ten-Tails and feeding upon the resulting God Tree's chakra fruit. When activated, it spreads grey markings along the left side of its body forming a pattern that almost mirrors Jigen's, extending to the left eye.

Momoshiki Ōtsutsuki

 * Boruto Uzumaki: Momoshiki embedded his Kāma into Boruto's right palm as the boy dealt a fatal blow to him using the Parent and Child Rasengan. When activated it spreads across the right side of his body forming angular and curving geometric patterns, extending up to his right eye, and then glows blue. Progressing further, he sprouts a horn similar to Momoshiki's and his right eye turns into a Byakugan. By the demise of Isshiki, Momoshiki's Kāma in Boruto was estimated to be 70% to 80% extracted.

Abilities
When activated, Kāma significantly enhances the user's physical abilities and the power of their jutsu, and can absorb chakra and chakra-based attacks like ninjutsu. Kāma can also be used as a medium for Space-Time Ninjutsu, opening rifts to any location including foreign dimensions at will. This ability seems to be rather advanced as only Jigen was able to use it by himself, Boruto and Kawaki's needing to cooperate to use it instead.

Boruto's and Kawaki's Kāma exhibit when in close proximity. When their Kāma resonate, it apparently enables them to release anything that either of them had previously absorbed. This resonance seems to be coming from Kāma that are acquired from different sources, as Kawaki got his from Isshiki (via Jigen), while Boruto got his from Momoshiki. Isshiki and Amado theorised that it was this resonance that allowed both Kawaki's and Boruto's Kāma to mature more rapidly than expected. Although Jigen is able to synchronise with Kawaki's Kāma to open a space-time rift, no such resonance exist between the two of them as Kawaki did not experience the sudden growth until his contact with Boruto.

Kawaki could activate it at will by the time he first met Boruto and three years later, Boruto was able to activate the seal at will as well, while Jigen was fully capable of activating it any time he desires. Boruto's resonated Kāma could also be forcefully activated when Kawaki activates his own nearby.

Through the aid of science, Isshiki was able to transfer his Kāma from Jigen to other individuals, albeit with a low rate of success, as of fifteen known test subjects, thirteen are confirmed to have died, with Kawaki the only known successful recipient. Jigen has also shown the ability to absorb chakra from creatures that are similar to tailed beasts and force Kawaki's Kāma to synchronise with his for him to open a portal to his location.

Manifestation
As noted by Code, a Kāma's boost of power to the user comes from subconsciously accessing all the accumulated experience of the Ōtsutsuki that branded them. As such, under certain circumstances the Ōtsutsuki can manifest their will to possess the body of the vessel, causing the markings to change shape and the surrounding portion of their body to transform, undergoing changes that may include protruding Ōtsutsuki's signature horns and even activating their dōjutsu. This seems to only be possible after a great deal of time or as a result of resonance, and typically only occurs when the vessel's chakra has been depleted to the point that they lose consciousness.

While Jigen can activate this state freely, Kawaki was only able to partially achieve it out of anger, with Jigen surprised by how quickly it progressed. Likewise, Momoshiki was only able to manifest through Boruto's body when the boy was knocked unconscious and nearly killed by Boro. Extended use of this form can greatly wear down the vessel's body: Momoshiki had to absorb Naruto's chakra to continue fighting until he killed Boro in Boruto's body and he soon collapsed. Additionally imperfect vessels can break down from the sheer power the Ōtsutsuki was using, as though Jigen could activate it willingly, he was unable to handle Isshiki's full powers for long and began breaking down after a while.

Resurrection
Over time, the vessel's own genetic information will be completely overwritten by the Ōtsutsuki biological data accumulated in the Kāma, at which point the Kāma will disappear and the Ōtsutsuki will resurrect, taking over the vessel's body and erasing their personality. This is the true purpose of Kāma, and allows the Ōtsutsuki to transcend death. Even if the vessel's body dies and is severely damaged and/or not fully compatible with the Ōtsutsuki, or the Ōtsutsuki is only partially manifested, so long as it exists and still bears Kāma, it will remain viable for the Ōtsutsuki to resurrect through, in which any damage it has suffered will be healed. Despite being reformed virtually identical to how they were in their previous body, the Ōtsutsuki also retains all the memories, skills and knowledge from the vessel.

Amado noted that there is no known way of removing a Kāma from a vessel, nor to stop its takeover, aside from killing the vessel before the resurrection process completes itself; even the very Ōtsutsuki who placed the seal onto the vessel cannot control the automatic transfer. However, the Kāma's final process of resurrection will not occur so long as the Ōtsutsuki in question is still alive, hence Isshiki was not reborn through Jigen's body despite the Kāma already having extracted all the data into Jigen's body. At the same time, a non-suitable vessel can be used to perform an imperfect resurrection of the Ōtsutsuki. Upon being resurrected, should there be any other Kāma implanted by the same Ōtsutsuki, those additional Kāma will simultaneously be erased. Amado speculates this is a safety feature to prevent duplicate incarnations of the same Ōtsutsuki. However, despite the Kāma's erasure, any Ōtsutsuki data that was already extracted will remain so. Also, White Kāma will not disappear if an Ōtsutsuki resurrects via a complete Kāma.

Though untested, Kawaki hypothesizes that he and Boruto may be able to produce Kāma of their own, as they have each already had in excess of 80% of their body overwritten by Ōtsutsuki genetic data. If proven true this could potentially allow Boruto to survive Momoshiki's reincarnation by subsequently reincarnating through a vessel of his own. Kawaki also theorises that Code, bearer of a White Kāma, would be an ideal candidate for Boruto to use as a vessel, as Code proved himself being compatible to survive the process while not being anyone's vessel. Amado claims to be able to restore Kawaki's Kāma, which would restore his access to the Ōtsutsuki powers in his body without the drawback of being taken over by Isshiki, as his soul has vanished.

Drawbacks
Imparting a Kāma onto a candidate vessel requires a huge amount of energy to do so; when Isshiki was fatally injured by Kaguya, he did not have enough strength to apply one to Jigen at the time. When applying a Kāma normally, it seems to have no detrimental effects on the potential vessel, whether they are compatible or not, as neither Jigen nor Boruto suffer any negative effects nor any apparent pain. However, when Isshiki attempted to place another one while inhabiting Jigen, he and Amado utilised a seemingly different method that involved scientific aid, in which Isshiki would activate the seal from Jigen, and spread it to a recipient, causing them intense pain and, if incompatible, the recipient would most likely die, as thirteen children died this way. It is also possible that a failure be instead be gifted the White Kāma, granting them the pure power of an Ōtsutsuki but not as a receptacle for the soul.

As Amado noted, the most important factor of applying Kāma is the selection of the vessel; if an Ōtsutsuki uses an inadequate vessel for a revival, the body will be unable to handle the enormous chakra, and most likely die within a couple of days. Compatibility seems to be rare, as out of the fifteen children Isshiki attempted, Kawaki is the sole success, and Isshiki himself noted how Boruto's affinity with Momoshiki's Kāma to be uncommon. Placing a Kāma onto a clone is ineffective, as the mark will vanish and will not transfer back to the original.

Once the Kāma is applied, its process of spreading the biological data into the vessel and the final resurrection initiates automatically, in which not even the caster can control it. When an Ōtsutsuki resurrects, the vanishing of duplicate Kāma means they're vulnerable to a permanent death unless they can apply another Kāma, especially if forced by circumstance to resurrect in an imperfect vessel.

Amado created a drug that weakens the Byakugan. He originally hoped to use it to weaken Isshiki, and theorises that this drug can stall Momoshiki from reincarnating through Boruto, as the Byakugan originates from the Ōtsutsuki, and weakening the kekkei genkai may slow the Kāma that is transforming Boruto's cells. Untested possibilities led Amado believe the drug may require constant intake, that deteriorating eyesight and even death may result, and he warned that Naruto must not allow Hinata nor Himawari take it.

An individual who has been given Kāma is viable to serve as a sacrifice for Ten-Tails, as they technically become Ōtsutsuki. It remains dependent on how much of the data is extracted onto the body, as Momoshiki determined that Kawaki was viable due to having 80% of the process completed. However, using such a vessel as a sacrifice will result in the tailed beast blooming into a God Tree of inferior size and a lower quality chakra fruit, as they are not completely Ōtsutsuki. Similarly, even if the data has been fully extracted but the vessel has yet to be reborn as Ōtsutsuki, if said vessel is incompatible with the Kāma to begin with, this will also result in the God Tree's reduced size and ability to produce a fruit.

Using Kāma in battle could prove taxing for less skilled users, even more so when they are already weakened, as Kawaki quickly collapsed after using it against Garō as he was already injured from defeating Kara's robots while Boruto was left so badly weakened after using it for the first time that he collapsed and had to be helped to return to Konoha. Additionally, activating it seems to cause a not sufficiently experienced user some pain, as Boruto expressed pain whenever he activates Kāma. Jigen doesn't seem to suffer these weaknesses as he is much more capable at using them than either Boruto or Kawaki, as he never showed any reaction when activating Kāma and using it in his prolonged battle with Naruto and Sasuke had no effect on him. However, one known weakness of the seal that even Jigen seems to suffer from is that incomplete vessels could breakdown from channelling Kāma's full power, as after overpowering Naruto and Sasuke, the blackened section of his body cracked and he even cried soon afterwards and was forced to retreat back to be treated by Amado.

Kāma can only absorb chakra-based substances, hence the wielder is vulnerable to non-chakra matter and energy such as viruses and natural flames.

Trivia

 * Though its furigana reading indicates the pronunciation, its kanji spelling is given as , a Japanese tool resembling a wedge or linchpin, and its full appearance when not embedded in a host's body has a similar appearance and function.
 * "Kāma" means "wish", "desire", or "longing" in Hindu literature, and in Japanese it is also an uncommon way to write "karma." The latter is used as its official translation in Western media.
 * Sarada Uchiha has theorised, due to their similar appearance, that the Strength of a Hundred Seal may be related to it.
 * Any Ōtsutsuki who intends to become a sacrifice for the Ten-Tails to bloom into a God Tree utilises Kāma to prepare a vessel beforehand, for their revival later on.
 * At 80% of data extraction in a vessel from a Kāma, Momoshiki believes this is sufficient to make the target a sacrifice for the Ten-Tails.
 * In the anime, Isshiki had also attempted to apply the Kāma on adults. According to Garō, a chance of survival comes at a cost, as he himself was chosen and survived, but at the cost of his right arm. However, Garō did not gain a White Kāma.
 * In the anime, the first time Momoshiki took over Boruto, he spoke in a mix of his and Boruto's voice. The second time, he spoke only in his voice, Boruto's voice only being heard when he began to take back control of his body.