Kāma

Kāma is a seal bestowed by members of the Ōtsutsuki clan that takes the form of a black diamond on the recipient's body, marking them as a and if successful a  for the clan member. As Kara solely holds all intel on the seal, the phenomena largely remains a mystery.

Known users

 * Jigen bears the mark on his chin as the current vessel for Isshiki 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.
 * Kawaki received the mark on his left palm through scientific experiments conducted by Jigen. 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.
 * Boruto Uzumaki received the mark on his right palm from Momoshiki Ōtsutsuki after dealing a fatal blow to him. 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.

Abilities
When activated, Kāma significantly enhances the user's physical abilities and jutsu's power. The Kāma can absorb, retain, and release an enemy's attacks like ninjutsu, and unleash large-scale explosions. 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 also seems to be independent from the origins of the involving Kāma, as Kawaki got his from Jigen, while Boruto got his from Momoshiki.

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. Using Kāma in battle causes Kawaki's body to overheat, leaving him unconscious. Boruto also collapsed after using it for the first time. Jigen has displayed the ability to use Kāma for a prolonged period of time but upon using the full power of the seal, even he suffers sufficient pain as to shed a tear and it has a unique effect of causing the blackened section of his body to crack.

Through the aid of science, Jigen can use his Kāma to transfer it 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.

Jigen and Kawaki's Kāma have shown an enhanced form where a horn protrudes from their left temple. While Kawaki was unaware of this and only recently activated it due to his advancement subconsciously, Jigen appears to be aware of this and is capable of activating it at will.

According to Jigen, when a person receives a Kāma, they become a vessel. So far, Jigen was confirmed as Isshiki's current vessel, Kawaki as the next one, and Boruto as Momoshiki's vessel. Jigen's words imply that not everyone can become a "perfect" vessel, exemplified by Jigen's body being unable to withstand the full extend of Isshiki's power for long. However, in the case of fittiing individuals like Kawaki and Boruto, the seal will apparrently transform the vessel into their respective Ōtsutsuki clan member.

Trivia

 * Although the kanji itself would normally be translated as, the furigana indicate the reading . "Kāma" means "wish", "desire", or "longing" in Hindu literature. In Japanese it is also an uncommon way to write "karma".
 * It has been theorised, due to their similar appearance, that the Strength of a Hundred Seal may be related to it.