Gaiares is a horizontal-scrolling shoot em' up released for the Sega Megadrive/Genesis in 1990. The game bears a striking mechanic similarity to that of the R-Type series, alongside those of other well-known Shoot Em' Ups such as Gradius and Thunder Force, all of which it was trying to compete against.

In the year 3000, the Earth has become a toxic and radioactive dump, leaving the planet rendered as an uninhabitable and polluted wasteland and driving the humans to near-extinction. The space pirates Gulfer, led by the evil Queen ZZ Badnusty, plan to harvest the pollution to create weapons of mass destruction. The United Star Cluster of Leezaluth sends a warning to the Earth about their plans, stating that if they could not stop them, they would be forced to supernova Earth's sun, those destroying the planet as well as causing the extinction of the human race; before having to carry out the process themselves; but if they succeeded (to switch Queen ZZ Badnusty doubted), Leezaluth would use their technology to restore the Earth to its former beauty. Dan Dare (Diaz in the Japanese original), a young pilot from Earth was chosen to be the pilot of a new fighter ship to combat the Gulfer. The ship is armed with a powerful experimental weapon from Leezaluth called the TOZ System, which would be operated by Alexis, the emissary from Leezaluth.