Danguard Ace (\"Planetary Robot\") centered around Earth\'s discovery of a new planet called Promete. Earth had become ravaged and almost uninhabitable due to overpopulation and a lack of natural resources, so a ship was sent to the remote outreaches of the solar system to explore the unspoiled Promete, which shared similarities with Earth\'s environment.

Unfortunately, the evil scientist Komisar Krell also discovered Promete, and he planned to move his own people onto the planet. After Krell attacked the first Earth ship journeying to Promete, the Earthlings built Danguard Ace to protect them from future assaults.