And it's dear companion piece.
Sakon and Ukon's Kekkei Genkai v3
Twin Cell Pulse
This kekkei genkai manipulates
cells.
By controlling cellular fusion and fission, one can grow copies of their own body parts to provide them with additional limbs that they can control like any other. They can create
hands and arms to grab objects, block attacks or punch an opponent,
legs and feet to provide extra stability or kick an enemy, or even create
another head that can perceive the world around them to cover one’s blind spots. These body parts can appear
anywhere on the original body near instantly then withdraw just as quickly and there is little limit on how many body parts can be created, making them incredibly difficult to predict as they do not follow ordinary human movement.
However the proportions of these limbs have to be exactly the same as the original as they are literal copies. Because they are connected to the original body, any injury inflicted on them causes the individual to fully experience that pain themselves which does not have any lasting effect once the copied limb is removed but it can be distracting. And if a copied body part is severed from the main body, it cannot be reattached or controlled any further.
This cellular control grants those who possess this kekkei genkai with a type of
accelerated healing by consciously splitting and fusing cells in response to the injuries they have suffered. This makes their recovery time far faster than ordinary humans and able to deal with injuries that others wouldn’t be able to without medical aid. However this feat does require focus and a significant portion of chakra which makes it unsuitable for combat situations so it is ideally only used after the battle has ended and cannot deal with
extreme injuries.
And an unusual trait of this kekkei genkai is that it is often possessed by identical twins who instinctively use their abilities on each other from an early age. They willingly
merge their bodies together with one of the twins becoming the main body while the other twin rests inside them, sharing one body and each other’s senses. Existing in this state becomes so natural that they spend practically their entire lives in the
same body.
The advantages of this body sharing is that any battle against them is two-on-one as the twins utilize unsurpassed teamwork to overcome their enemies.
By acting in unison, they can simultaneously attack and defend without needing to consciously focus on both actions as each twin acts independently both from the same body. The resting twin is able to separate their body parts from the active twin, allowing them to extend their hands to punch or grab or their feet to kick out or even their head to see from an entirely different angle. Merging can even aid in their self-healing ability as the synergy between their kekkei genkai helps accelerate the process further and the injured twin can
hide within their sibling to avoid further damage.
However, twins often become too reliant on each other’s support which can be a significant disadvantage when they are separated. The active twin is more vulnerable to blind spots and has lower defences in combat, and the resting twin
lacks the stamina and focus for protracted fights. At the same time, they are both unaccustomed to using their kekkei genkai to replicate their own body parts like the rest of their clan since they would ordinarily perform that role for one another which arguably makes them less dangerous when separated.
The ability to merge bodies is not actually limited to twins and can be performed by any two individuals who possess this kekkei genkai. But this is usually just a temporary measure to aid in combat to make them into one, stronger unit with a hidden trump card rather than a permanent state. There are no known cases where three or more individuals have successfully merged together, even among siblings.
When combining their abilities with ninjutsu, one can perform much greater feats such as creating entire clones of flesh directly from their body to act in concert, grow body parts from the surrounding environment rather than their own body or even
forcibly merge with an enemy by breaking down their own body on a cellular level and
enter their enemy's flesh, then they
corrode the cells of their host to essentially consume them from within and recreate their own body. While these are rare and advanced skills that few possessed, it was enough to give this kekkei genkai a sinister reputation among those with such knowledge.