Once upon a time, Earth launched a united space force far beyond the outer reaches of the solar system. Using Bio-Cyborg machines, this Imperial Earth Army soon formed an oppressive dictatorship. Appalled by the injustices being done in the name of law and order, a group of freedom fighters rebelled and developed a method of capturing and controlling the Bio-Cyborgs, setting off a space battle the likes of which the universe had never seen before.
At the helm of a Garland spaceship, you fly and shoot your way through five stages to free Earth from oppression and tyranny with no power-ups for upgrading your ship or its basic Beam Vulcan weapon. However, your ship is equipped with a Tranquilander, which you can use to stun and take over Bio-Cyborgs. Once in control of a Bio-Cyborg, you can use its weapons. The Baron has a Sonic Gun and Diffusing Bomb. The Neptune is equipped with a Wide Laser and a Hyper Bomb. The Odyssey comes with a Funnel shot. The Mars has a Mega Cannon and an Atomic Shield. The Titan sports a Slice Laser and Homing Missiles. The Hyper D uses a Beam Gun and a Vertical Shield, and the Shadow Blade has a Twin Cannon and a Dimension Field. You can only control one Bio-Cyborg at a time.
Each of the five stages in Blazeon is teeming with Bio-Cyborgs for you to shoot or take over, and each stage has a middle and final boss. Like most shooting games of this type, the action moves from left to right.