However, after hundreds of peaceful years, the Iridion Empire returned and attacked the human colonists with the intent of retaking their planets.

The player assumes control over the SHN-27 en route to save mankind from the Iridion once more.

In Story mode, the player follows a plot involving the defense fleet chasing the Iridion forces through five different solar systems in three areas each, although each area is symbolized as a planet (including asteroid belts and space travel zones).

The player can also use the Power-ups to empower firing strength or replenish the ship's armor.

The green power-ups also increases the shot count by adding two Satellites (or Options) that saddled alongside the ship.