War of the Gargantuas (1966).
Young female scientist Akemi is doing research on a recently discovered missing link – called a Gargantuan. It is docile and playful, but does manage to escape into a nearby mountain forest. Soon after a giant behemoth is seen rising from the nearby ocean attacking all it sees. It looks like Akemi’s beast, only it is green. In the resulting confusion, the army finds and attacks the good Brown Gargantuan. The Green Gargantuan soon comes to his brother’s aid, but flies into a destructive rage. It is up to The Brown One to take on his brother in a destructive fight to the finish in order to end the Green Gargatuan’s rampage!
Directed by Ishiro Honda. Starring: Russ Tamblyn, Kumi Mitzuno, Kenji Sahara, Nobuo Nakamura. (92 mins).