The Sairin clan embrace the true art of assassinations and shinobihood. They are considered masters of stealth and secrecy and have even gone so far as to protect information from each other and from the village itself.
The idea that "to speak is to bleed" is something preached from the very beginning of the clan itself, and is a phrase that means to give up information to anyone is the same as giving up your weaknesses and will only lead to one's own demise. This practice exists within the everyday lives of the clan. Despite them even keeping secrets from each other, the clan seems to function normally and has existed for a few dozen years.
45 years ago, a group of like minded individuals formed a pact and got together to share their secrets. They established the foundation for what later became known as the Sairin clan, however only a year later the individual whom was known as the clan leader was assassinated. The clan was still new and hadn't made any enemies during the year they existed, so they all came to the conclusion that it must have been one of their own who had done it. Despite all the questioning, none of them admitted to the crime. They soon became paranoid of one another and began to spy on one another in their own clan compounds.
This went on for the better part of a few years before one of the children came up with the idea that to speak is to bleed. He explained that for any one member to give up any information they knew would more than likely result in the end of their life, and that would only create more strife within the clan and would lead to its own demise. Though the clan members were still wary of one another, they agreed to this idea and decided to keep to themselves.
Rather than fight amongst one another, they began to train themselves in order to better their shinobi skills. Their skills earned the respect of a nearby village, Amegakure, and they were invited to join if they pledged their loyalty. They did so in a round about way and moved into the village.
While in the village, one of the clansmen gained inspiration from the rain and the clouds and invented a set of techniques which would later become known within the clan as the Yamaji no Jutsu. There were many who sought to learn it from him, but he would not spill any of his secrets and trained alone in the art. This earned the ire of his kin and so they would spy on him in an attempt to learn its secrets. Those he found spying on him he would attack without the intent to kill, and so members of the clan began to train in their art of stealth in order to try and learn the jutsu without being caught.
This greed to learn the Yamaji no Jutsu lead to the clan, over the course of decades, to become incredibly versed in the art of stealth and spying, while those who did manage to learn the techniques become well versed in the art of assassinations. To this day, the Yamaji no Jutsu has never been taught to anyone clan member, but has been learned through spying.
There exists no real hierarchy in the clan. There is no head, no heir, no council or anything like that. All in the clan are equals. Each member of the clan simply governs themselves, and the only time one would actually take orders from another would be from their parents or a superior ranking shinobi. If the clan had a real leader, no one would ever know who they were or that they even existed.
Yamaji no Jutsu
The clan possesses the ability to use a set of secret techniques known as Yamiji no Jutsu. It allows them to produce a black fog composed of raw chakra and manipulate it into various forms. The fog, while normally vapour in form is easily susceptible to shape manipulation and can become a liquid or a solid depending on the jutsu used.
The black fog is usually prepared before hand and sealed away within the clan's personal stylized seals on the palms of their hands, but the seals are not limited to being placed there. This is because the black fog usually takes time to create, as it requires one to manipulate their raw chakra into a completely different form.
How much can be stored, and/or created would be based on: experience(rank), chakra reserves, and clan expertise.
One's rank sets a standard for how much, but additional Special Abilities play a factor. Some notes: A clansmen cannot perform an S-rank technique unless they have the reserves. This does require a sense of clan expertise, and personal reserves. If someone is lacking in either, they'll fail to truly fuel very high techniques.
One can assume two lesser techniques can equal one higher in strength. This is just a fair presumption I go by, a recommendation and a good way to gauge yourself. This scale is the bare minimum, assuming one is -not- an expert in the clan, does not have higher chakra reserves and based purely on ranking standards.
Academy: One very low technique
Genin: Two very low techniques[One Low]
Chuunin: One low technique, and one very low technique.
S.Jounin: Two low techniques(One Medium)
Jounin: One medium technique, and one low technique.
Elite Jounin: Two medium techniques(One High)