A mysterious alien spaceship crashes into Graviton City, erasing the population and leaving a massive crater that the city rebuilds around over time. Sixteen years later, a new school year begins for two transfer students at the all-girls Graviton High: A-ko Magami, Miki Ito a lively, red-haired, sailor-suited teen, and her best friend C-ko Kotobuki, Michie Tomizawa a bubbly, carefree optimist. Although A-ko seems to possess superhuman speed and strength, she still believes she’s just an ordinary teenager, mostly worried about getting to class on time because she chronically oversleeps her alarm.
The pair quickly draw the attention of B-ko Daitokuji, Emi Shinohara a rich, snobbish, brilliant fellow student who becomes obsessed with C-ko and determined to win her over. B-ko’s schemes begin as a series of increasingly formidable mecha piloted by her teammates, launched at A-ko each morning. After losing each new, more powerful machine, she ultimately unveils the Akagiyama 23, a bikini-clad powered suit, and the battles spread through the school with growing ferocity and little restraint.
Meanwhile, trench-coated spy D (Operative DC138621-S113), Tessyo Genda has been watching A-ko and C-ko every morning, relaying information to a large approaching spacecraft. The aliens conclude they have found a lost princess they have been seeking. They arrive on Earth and unleash an all-out assault against the Graviton military, which struggles to counter the alien technology. The fight between A-ko and B-ko continues to spill across the city even as the military and aliens clash, and in the midst of this chaos, C-ko is abducted by D, revealed to be a member of the Lepton Kingdom of Alpha Cygni—an all-female alien race. C-ko is their princess.
Witnessing the kidnapping, A-ko and B-ko set aside their rivalry and infiltrate the spaceship. Inside, A-ko confronts D and the ship’s alcoholic Captain Napolipolita, Shuichi Ikeda while B-ko rescues C-ko. Yet the truce dissolves when B-ko opens fire on A-ko, D, and the Captain, destroying the ship’s navigation system. The vessel crashes onto the city’s Military Command Tower (the remains of the earlier crash). After the ordeal, both A-ko and C-ko find themselves perched atop an unconscious B-ko.
The next morning, A-ko wakes up sore but cheerful, and she and C-ko walk to school in new uniforms. They pass a disheveled D and the Captain begging for donations to repair their ship. The film closes with B-ko’s sly smile as A-ko appears on the horizon, hinting that their adventures—and their rivalry—are far from over.
