Twelve years ago, an alien force known as the Heterodyne attacked earth. In a defensive response, the government contracted to have a robot built to help defeat this monstrous foe. The contract was awarded to the lowest bidder, the Heterodyne never reappeared and now the idle unused Dai-Guard has been assigned to the corporate marketing department as the central attraction to a theme park. And when a Heterodyne does reappear, it falls upon three marketing department employees to activate the Dai-guard robot and engage the enemy. The rash and impulsive Akaji and a reserved and refined Aoyama, team up with Ibuki, a long time coworker and friend to engage and defeat this alien enemy. With a profit/loss margin in mind, the company decides to create a new marketing department sub-unit, designed to use the Dai-Guard robot in the defense of Japan.