Ketsueki

The River of Blood
In the beginning, Hiroto Ketsueki was thought to be a ruthless and cold killer; heartless and in need of destroying. Many tried to claim his head, but all fell to his feet. He was a "monster," they screamed- an "unholy terror brought to earth." How could a human be thought of in such a way, or act so vile that he was cast out of every known village known to the Shinobi Realm? Hiroto was part of a group that wished only to cause as much destruction and devastation as possible before they died. Why? Because they could. Legend goes that the group was so odious and malicious that when they stumbled across a tree (nicknamed "Tamashī no Ki," or "Tree of the Souls") that granted them powers beyond their wildest dreams.

The tree was said to be evil, for it was even rumored that it grew upon a once battlefield in a river of lifeblood. The tree harbored an Angel that had fallen from Kami's grace, so was sealed away in this tree, never to be heard from again; at least, that's how the story was always told. The tree, which held no leaves, and whose bark was pitch black, granted the group of six the gift of life. By ingesting a mouthful of the Chi no Kawa (River of Blood, 血の河), the six men all followed the instructions given, only to find themselves in unbearable pain, which lead to the "extraction of their souls." When the awoke, they were nearly immortal. Arrows which pierced their hearts held no meaning, for the hole in their heart sealed back; the limbs, even after being chopped off, regrew as if by magic; and no amount of damage done to them could be deadly.

Birth of a Superhuman
This story has been passed along the Ketsueki bloodline every generation, and it never changes. In actuality, however, Hiroto was the elder of this bloodline, who died several hundred years prior to the present day. He was born a normal child, or so his parents thought, but he was granted a unique body, one that scientists and Medical-nin alike were baffled by. The peculiar little boy, much like a starfish, was granted Totipotent Stem Cells, or immature stem cells, which are capable of transforming themselves into any cell in the body, making it possible for regrowth. The only cells they cannot regenerate are those located in the brain.

He started out being only able to heal small wounds on his body, and anything more serious had to be handled by a professional healer. The older Hiroto got, and the more injuries he received, the greater his ability to heal became until even internal injuries, which would be fatal to any mere mortal, was healed in seconds and limbs could be regrown.

As time wore on and he settle into a family, the next member of the bloodline came into life with the same sort of genetic mutation. Before long, an entire clan became populated, and was known as The "Ketsueki" Clan, or the "Blood" Clan.

Currently, the only known living user of this Kekkei Genkai is Ushinatta, whose whereabouts are unknown, though it is possible there are others.

The Developing Abilities
As the clan grew larger, more and more people were born with this genetic mutation. Boys, or girls, mattered not, for all had a high chance of receiving this trait. Those that were born with it curiously began to develop mental instability, though it is currently unknown as to why that is. Some members consider it a curse, and more often than not the users of this Kekkei Genkai show a blood thirsty tendency, which many believe stems from their clan being that of hardened warriors; the need to fight is there as a constant.

Their abilities begin with simple healing abilities granted the same as everyone's, but in a more swift process. Scratches, bruises, and scrapes will be gone within a few minutes after receiving the wound, but larger wounds will take hours, and afflictions of an even greater magnitude will take even longer; however, the user cannot die from wounds such as these.

A more advanced user, such as those at a Jōnin rank, can begin regenerating lost digits. Not only this, their healing factor is increased as well to where small injures healing in seconds, larger wounds in minutes, and broken bones in hours; albeit, internal injures can take up to a day's time depending upon the severity and amount of actual afflictions.

A master is nearly indestructible. Limbs regrow within a matter of minutes, small afflictions instantly vanish while larger ones are gone in seconds, and so on through minutes, but it will never take an hour for a master of the Kekkei Genkai to heal.

Chakra is not required for this healing because it is a Genetic Mutation and nothing more. There are no other pluses to this Kekkei Genkai, which means there is no large chakra pool or inhuman strength, for this ability came from a genetic mutation of Stem Cells, causing them to be permanently immature and become whatever the body needs; consequently, there are no other trumps from this clan.

Albeit this is true, their blood also has the ability to heal others, but the regenerative properties are fictitious. Any wound can be healed, but at a slow rate compared to the user's, and without the regeneration plus.

Appearance of the Members
If this bloody barbarianism could be looked past, it could be seen that these users resemble otherworldly beings with their inhuman perfection in appearance. Flawless skin, brilliantly colored eyes that normally don't vary far in hues of red or golden, and hair that's silk in feeling with dark hair (normally black). Their height is average, though their weight is usually low; most female members can be found to be underweight.

Curse from Kami
As a member of this clan, there are two major drawbacks; whether there are more is currently unknown, but will be added here as discovered. The first and largest of the two is the Kekkei Genkai's limited ability. The only portion of the body that cannot be healed or regenerated on the user is the head, or brain. Stem Cells cannot multiply in the brain, therefore they cannot heal the brain from injury. In other words, if you cause enough brain trauma, or decapitate one of these clan members, they will be dead, period.

The second drawback is the curious development of psychiatric disorders found within the clan, though it doesn't seem to stem from just one disorder. The Personality Disorders and Mental Disorders in this clan have left many nothing but raving fools. The following are the most prevalent as of late:

Bipolar Disorder

Schizophrenia

Dissociative Identity Disorder

Oppositional Defiant Disorder

These disorders appear most often and in either gender, but this is not to say other disorders don't become apparent as well. There was even one instance of Pica, a compulsive eating disorder.