Space Pirate Descal conquer Earth in 2005. In 2500, a resistance group travels back in time to 2005 to collect the 12 Cosmo Capsules and prevent Descal's rise to power.

The finale of Toho and Konami's Chou Sei Shin Series, Chou Sei Kantai Sazer X debuted in 2005. In the year 2500, the Earth has been conquered by an evil race of Space Pirates known as "Neo-Descal" and covered in eternal darkness. With no other options left, the last remnants of Earth's armada send three of their ships through a wormhole that takes them back in time to the year 2005. According to the history books of the future, this was the year where three legendary Space Pirates from the "Descal" fleet conquered Earth by capturing the twelve mystical Cosmo Capsules and using their power to plunge the world into darkness. For the sake of averting this Bad Future, the heroes of the future recruit a modern man (Takuto Ando) to complete their Power Trio and form the Super Star Fleet, Sazer X.—TVTropes

In the year 2500AD, the Earth has been covered in a smog of eternal darkness, giving birth to a race of Space Pirates that have begun to conquer the galaxy, leaving each planet in ruins. With no other options, the remaining resistance devise a plan to use a wormhole to travel back in time and change history so that the Earth was never consumed by darkness and the future can be saved. This team is known as Sazer-X. Their mission is to collect the Cosmo Capsules; twelve items of great power that are scattered throughout Earth in the year 2005AD. When all twelve are gathered, they grant one wish to their owner; it was this wish that doomed the Earth to an eternity of darkness. Sazer-X must gather all of the Cosmo Capsules before history has a chance to repeat itself.—Crunchyroll

The last of the Chouseishin series, it opens to Earth in the year 2500 when it has been taken over by a group of space pirates known as Neo-Descal. The remaining members of the human resistance send their trump card weapons, the three Ryuuseishin warships to the past to try and change the future by defeating Neo-Descal's ancestors, the Descal fleet, when they invade Earth in 2005. Along with the Ryuuseishin comes Ad, captain of the Adle-Eagle squad and his right-hand man, Gordo; Kane, captain of the Beet-Vizor squad; the twin Sazers Ein and Zwein; and Remy, who pilots Great Lio. Ad and Kane are joined by Takuto Andou, whose grandfather met Captain Shark, leader of the resistance, as a young man and was left with a Knuckle Cross to allow his grandson in 2005 to become the third member of the team known as Sazer-X.