Once, a sophisticated robot successfully defended the planet from alien invaders. Over time, people forgot how to operate the colossal machine, leading to its abandonment in a remote location. Despite this, the Doctor remained determined to locate a capable pilot for the robot. Unexpectedly, the robot became a gathering spot for a group of eight middle school girls, who affectionately referred to it as "RoboSan" and disregarded the Doctor's warnings. Then, a sudden invasion by powerful robots from a foreign military group shook the city. The dormant robot suddenly sprang to life.