Most humans do not know that every person is one of three doppel liners, three people who share the same fate, and that god-like beings, the Tera Guardians, that protect the natural balance of power in the world. However, Keita Ibuki, a videogame programmer from Tokyo, is suddenly drawn into the intrigues of these powerful beings during a chance encounter with a girl named Kuro, a young Tera Guardian who makes a contract with Keita in order to save his life.