Godzilla Vs Uchujin was intended to kick-off the Millennium Series the film was planned for a 2000 release, instead of Godzilla vs. Megaguirus.
The plot was An astronaut returning to Japan has unknowingly been infected with a strange alien virus. As he starts to mutate, he runs off to hills, in order to protect his daughter from himself. After he becomes giant-sized, the mutated man-beast learns that Godzilla has returned to attack Japan. He rushes to defend his daughter, who is at the heart of Godzilla’s rampage, leading to a monster slug-fest.