Twelve years ago, the Earth was attacked by giant invaders. To defend our planet, the Earth's greatest minds and corporations assembled to design a giant robot of incredible power. Unfortunately, as with most government projects, the contract went to the lowest bidder. Fortunately, by the time the robot was ready, the mysterious invaders had already disappeared without a trace.

The giant robot became first a curiosity, then a tourist attraction. But now the invaders are back and the only thing in their way is Dai-Guard and a young team of office workers who've been supplementing their regular incomes as part time pilots and tour guides. Can these reluctant heroes halt their alien foes while simultaneously concealing the defects in their giant robot?

講述主角仲村葉本身是女子力高的OL，實際上自小已經是特攝片的狂迷，因為被母親禁止變成隱性宅女，之後遇上了同樣喜歡特攝的吉田久美，讓她決定向母親公開自己作為宅女的身份。