Summary Act I

Two young and beautiful girls, Cobalt and Sepia, are speaking about the invasion of Earth in a room aboard a gigantic Cthuwulf spaceship. Cobalt is sent to Earth aboard the Delos Theta, a powerful robot, to stop Iczer-One and prevent her from finding her human partner.

Nagisa, a normal human girl, is going to school when she meets Iczer-One who seems to be waiting for her on the side of the street. She exchanges a few words with her but when she want to show her to a school-friend, Kawai, who has just arrived, Iczer-One seems to have vanished.

At school, Nagisa has an exam but she seems to fall asleep in the middle of it and "dreams" that she is alone with her friend Kawai when this one suddenly turns into an horrible monster. Iczer-One seems to be looking over Nagisa from outside, floating into the air. Suddenly Nagisa "awakes" in the middle of the test, very confused.
A little while later, she is speaking with friends on the roof of the school when they suddenly all turn into monsters. Nagisa falls from the building but is rescued by Iczer-One who suddenly appears in middle-air. Nagisa flees from Iczer-One screaming and is transported into another dimension where she is attacked by monsters and faint. She is rescued once more by Iczer-One who destroys the monsters.

Nagisa

When Nagisa awakes, she is in her room without knowing how she arrived there. During the night, Iczer-One seems to keep watch over her but shortly before dawn, Iczer-One is attacked and finds herself trapped in another dimension.
When Nagisa wakes up, her mother and father transform themselves into nightmarish monsters and attack her.
Iczer-One is hard pressed to defeat the new type of Void that attacks her but she finally finishes it and comes back to our dimension where she is forced to kill Nagisa parents, now totally and irrevocably transformed into monsters. Nagisa accuses her of all that is happening and of the death of her father and mother.

During that time, Cobalt, aboard Delos Theta, lands in the middle of the city. The army tries to push back the invader with their latest battleship, the Fuji-1, but they don't stand a chance against the power of Delos Theta and are quickly destroyed.

Iczer-One has noticed the landing of Delos Theta and she calls Iczer Robot to fight it. She brings a still screaming and reluctant Nagisa into the Robot to fight with her as her partner.
Nagisa still refuses to fight to protect the Earth and Delos Theta seems to be wining against Iczer Robot. Finally Iczer-One persuades Nagisa to fight, if not for her home world, but to avenge the death of her parents. Iczer Robot, piloted by Iczer-One and with the energy of Nagisa, quickly get ride of Delos Theta.