The Robot Girls Z; Z-chan, Gre-chan, and Grenda-san, protect Photonic City from the threat of Baron Ashura and her Underground Empire of Mechanical Beast Girls, usually destroying the town in the process. Ashura's boss, Dr. Hell, creates more Mechanical Beast Girls to fight against the Robot Girls, but each attempt results in favor. Later, the Robot Girls are attacked whilst helping out on a fishing boat.

Team Z are challenged to an athletics showdown by Team T to determine who should be the city's protectors. Later, Ashura uses a disguised Mechanical Beast Girl named Minerva X to try and disrupt the Team Z's teamwork by getting close to Z-chan. Afterwards, whilst relaxing at a hot spring, the girls meet idol Youko Lorelei, whose performance is interrupted by the Underground Empire's Mechanical Beast Girl, Belgas V5, causing whoever listens to it to become drunk with good feelings.

As Ashura finds herself unemployed after being laid off by Dr. Hell, Doublas and Garada are given a giant robot by a mysterious stranger to allow Ashura to have a final battle against Team Z. Although the mech completely overwhelms the girls, it turns out to be running on a trial version, which soon leads to its defeat. Later, a new enemy known as The Great General of Darkness-ko appears and steals the city's photonic energy, bringing it to its destructions and completely overwhelming Team Z. They are aided by the arrival of Team G, Steel Jeeg and Getter Robo, along with all their other allies, but are still overpowered by Darkness-ko. However, thanks to Ashura exposing her weakpoint, Z-chan manages to pull apart Darkness-ko's suit and expose the true mastermind, Mycenae-tan, who is swiftly dealt with.