is a Japanese space opera

Space opera

Space opera is a subgenre of science fiction that emphasizes romantic, often melodramatic adventure, set mainly or entirely in outer space, generally involving conflict between opponents possessing advanced technologies and abilities. The term has no relation to music and it is analogous to "soap...

 role-playing game

Role-playing game

A role-playing game is a game in which players assume the roles of characters in a fictional setting. Players take responsibility for acting out these roles within a narrative, either through literal acting, or through a process of structured decision-making or character development...

 released in 2004

2004 in games

This page lists board and card games, wargames, miniature games, and table-top role-playing games published in 2004. For video and console games, see 2004 in video gaming.-Game awards given in 2004:...

.

After the galactic catastrophe (called ), mankind lost great technology and interstellar civilization. At last, mankind had forgotten a presence of Earth, their birthplace planet.

Player characters are called "Retainers". Retainers seek humanity's ancestral planet, the Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 like as E. C. Tubb's Dumarest saga

Dumarest saga

Dumarest of Terra is a 33 volume series of science fiction novels by Edwin Charles Tubb. Each story is a self-contained adventure, but throughout the series, Earl Dumarest, the protagonist, searches for clues to the location of his home world, Earth....

 or Isaac Asimov

Isaac Asimov

Isaac Asimov was an American author and professor of biochemistry at Boston University, best known for his works of science fiction and for his popular science books. Asimov was one of the most prolific writers of all time, having written or edited more than 500 books and an estimated 90,000...

's Foundation and Earth

Foundation and Earth

Foundation and Earth is a Locus Award nominated science fiction novel by Isaac Asimov, the fifth novel of the Foundation series and chronologically the last in the series...

. A name of "retainer" means that he/she retains a qualification and abilities to find Earth.
Retainers' foe are named "Removers". Removers are trying to remove the memories and presence of Earth and prevent searching for it.

The setting includes Galactic empire

Galactic empire

Galactic empires are a common trope used in science fiction and science fantasy, particularly in space opera. Many authors have either used a galaxy-spanning empire as background, or written about the growth or decline of such an empire...

, interstellar police, space pirates, many planets that have strange cultures and environments and other science fiction

Science fiction

Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

gadgets. Many of the settings come from westerns and Japanese science fiction.