Gatchaman is based on a popular anime franchise of the same name created by Tatsuo Yoshida in the early 1970s.
In the movie, a mysterious organization calling itself Galactor declares war on Earth and overwhelms mankind. With half the planet occupied, Dr. Nambu of ISO (International Science Organization) calls upon five people who have received special training since childhood to act as the last hope of mankind: a team of superheroes called Gatchaman.
