"Outlaw Star" is a space opera/space Western set in the fictional universe. During its past, an asteroid containing a material known as "dragonite" crashed in the fictional Arashon desert of northern China. Scientists found that the dragonite contained properties related to "ether", an energy source that would allow spacecraft to travel faster than the speed of light, and thus traverse large distances of the universe in a short time. As new colonies were formed throughout the vast reaches of outer space, pirates, assassins, and outlaws began to threaten humanity's new frontier. To create order, the Earth Federation established four empires: USSA, Einhorn, Piotr, and Tenpa. However, internal power struggles within the factions and conflicts amongst one another become abundant, leading to inevitable lawlessness. The storyline starts shortly after an infamous outlaw named "Hot Ice" Hilda flees from the Kei Pirates, a branch of the Tin'Pa. Hilda has stolen from them a highly-advanced prototype ship dubbed the "XGP15A-II" and a suitcase containing a bio-android called Melfina, the only being capable of interfacing with the ship.