The Earth is being invaded by aliens. Fortunately, the aliens are so concerned about budgets and the cost of the invasion that they haven't succeeded yet. To defend the Earth, Dr Kishida has designed ARIEL, a giant robot shaped in the likeness of a woman with body-armor. Unfortunately, he has selected his relatives (his grand-daughters Aya and Kazumi Kishida, and his niece Mia Kawai) to be the pilots, and they are far more interested in their own lives.