A sci-fi franchise paying homage to the Super Robot series of the 70s and 80s.
Aquarion focuses of the conflict between humans and Shadow Angels. 12,000 years before the beginning of the series, humans live under the reign of the Shadow Angels, until Shadow Angel Apolonius falls in love with Selaine, a human woman. Together they use the legendary mecha Aquarion to overthrow the Shadow Angels. A decade before the series, humanity is once again attacked by the Shadow Angels, who harvest the humans for substance for themselves and the Tree of Live. The humans are harvestest by Harvest Beasts, who are guarded by Cherubim, robot soldiers of the Shadow Angels.
The discovery of the highly advanced Vectors (three jets that make up Aquarion) allow for humanity to fight back against the Shadow Angels. Just prior to a harvest attack, homeless boy Apollo comes across the pilots of Aquarion, Silvia and Pierre. It appears that Apollo is the reincarnation of Apolonius. The Shadow Angels then attack, and when one of the pilots (Reika) is unable to fight, Apollo takes over and they defeat the Cerubim, but not before the Harvest Beasts escape with Apollos friends.
Apollo is taken back to Aquarion headquarters DEAVA (Division of Earth Vitalization Advancement) as he might be needed for future fights with the Shadow Angels. The pilots learn how to work together and use the different Aquarions (depending on how the Vectors merge). Meanwhile, the Shadow Angels continue their attack against humanity.