Jūnikei

is a misterious organization. It is composed of master thieves and S-rank criminals that specialize in all sorts of crimes, even though they mainly focus on robbery, theft and sabotage. It is one of the main antagonistic forces during the series, as its members were introduced through the series as great threats to the world.

While its name refers to as "twelve meridians", the organization is comprised of thirteen members, numbered from zero to twelve depending on their power, although the leader will always be marked as zero, even though his/her strength may or may not be the biggest on the group.

Even though everyone works by itself, they can join forces with one or more fellow members, creating a stronger group that most of the time compliments their skills.

For a new member to arrive to the organization, one must first find out how to contact the headquarters. Following that event, they can either kill an existing member or wait for a new spot to appear (that can be created through any means). However, the shinobi that intends to join must have knowledge over the group's specializations, such as theft and other crimes, as well as strength and skill to perform any tasks delegated.

Rank Tattoos
Every member of the group possesses the same tattoo. It is a black spider with twelve legs. On its back, it possesses a number from 0 to 12, representing their power rank, twelve being the lowest and zero the number of the leader and the strongest. Usually, the members have it tattooed on their back, although some havve it elsewhere. Its size also varies, even though the smallest one was the size of one's palm.

Trivia

 * The name of the organization refers to The Twelve Meridians, the paths through which the life-energy known as "qi" flows, in traditional Chinese acupuncture. Each meridian takes care of an organ, that together form a living organism, a reference to the organization and the fact that it can only work if all of its members are kept.