Kurokami: The Animation (2009)

Blurb:
A world in which one’s happiness and misfortunes, even their lives are controlled by “luck”… In this world, there are three identical looking people in existence. Each of these three split between them an energy-like force called “Tera.” This energy can be attributed to the amount of “Luck” or “Life Energy” that an individual possesses.

Between those three, the one with the largest share of Tera is called the “Root” and the two possessing a lesser amount are called the “Sub.” If a Sub should ever meet up with another person that looks just like them, they will die. Their Tera will then be absorbed by the remaining two. If two Subs run into each other, they both perish, leaving the entire amount of Tera to be absorbed by the Root. That individual then becomes a “Master Root” and comes into possession of an enormous amount of luck and leads a life with success at every turn. This is the hidden truth of existence in the World of Humans and is called the “Doppeliner System.”

In accordance to the rules of the Doppeliner System, there exist beings who observe the human world, maintaining the balance of Tera, known as the “Coexistence Equilibrium.” These beings possess abilities that surpass those of normal human beings, and reside in hiding in places known as the “Pure Place” in tribes. They are called the Tera Guardians. This is a tale of battle that begins with the meeting between a human boy named Keita and a young Tera Guardian girl named Kuro.

Source: www.anisearch.com/anime/5087