Danguard Ace takes place on a future Earth in whichnatural resourceshave been depleted. People have begun looking toward other planets to survive, in particular to thefictional tenth planet, Promete. Although people had hoped to peacefully settle there, disaster strikes as the first explorers are destroyed bybetrayal.
After this event, an individual named Mr. Doppler leaves toward Promete on his own ship and declares himselfChancellorof the planet. Using Promete's resources, Chancellor Doppler constructs a vastmilitary forcegreater than that of Earth's. He forbids anyone from approaching the planet, under theinsanebelief that only he is entitled to it.
To gain control of Promete, the governments ofEarthbegin constructing massive combat robots. Doppler is able to attack and destroy all of them before they are completed, except for Danguard Ace. The forces sent to attack Danguard's base were destroyed because of the efforts of Captain Dan. Nothing is known of this mysterious man, except that he previously served Doppler while undermind control.
Takuma Ichimonji, son of the man who betrayed the initial Promete exploration team, becomes acadetat Danguard's base. Ichimonji hopes that he might restore his father's honor by fighting against Doppler's forces.