Gall Force: Eternal Story is a game that tells an additional tale from the Gall Force anime series, a series which revolves around a galactic battle between the all-female Solnoids and the race known as the Paranoids. This game tells the story of Rabby, the second-in-command of the space cruiser Star Leaf, having to rescue her six crew mates and also destroy the fortress of the Paranoids.
The game is a vertical scrolling shoot-'em-up. Players start by flying over the surface of the planet Terra, dodging and destroying enemies until they reach a set of launchers. Each launcher launches the player's ship into a different section of outer space. Each section features more shoot-em' up action until at the end a boss enemy appears. Defeating the boss enemy of a space section will release one the kidnapped crew members from bondage and allow them to rejoin back onto the Star Leaf crew.
Once a crew member is rescued they can be selected and they will transform the Star Leaf and use their own unique powers. Their powers typically affect on how the Star Leaf fires its' weapons. There are other power-ups that can collected such as the crash star that clears the screen of enemies, the barrier which provides the Star Leaf temporary invincibility, and the speed up icon which lets the Star Fleet maneuver faster than usual.
At the end of the game there is a message that mentions that Hal Laboratory's next game is titled Air Buster. This message is most likely making a reference to the game that was eventually titled Air Fortress.