Screenplay written by Shinichi Sekizawa
Alein invaders plan to scour the earth of its despoling population of humans before the world can be polluted beyond repair and becomes useless for their plans of colonization. Towards this end, the aliens bring the monster Mogu, Gigan and King Ghidorah to destroy human civilization. But their arrival does not go unopposed. The monsters Godzilla, Rodan and Varan escape from Monster Island to confront the alien space monsters.
After his bad reaction to Godzilla vs the Smog Monster, Toho producer Tomoyuki Tanaka ordered that a
new script be produced for the next Godzilla movie, this time featuring his classic foe, King Ghidorah.
The Return of King Ghidorah was one of two scripts submitted and contained many of the elements that
would later become Godzilla on Monster Island.