Toward the Vast World...
: Ep 1 -
Because of an accident in her scientist father's lab, a twelve-year-old girl, Kurau becomes possessed by a Rynax, an energy being that lives in pairs, and the personality of the little girl disappears.
A now adult Kurau, works as an agent, which is essentially a private detective. She has special Rynax powers which make her an unbeatable agent. However, Kurau is lonely, because she has not yet found her pair.