The movie was planned for a 1972 release, but didn't work out. People think it had to do with something to do with all the Kaiju baby making.
The Plot was
A creature from the moon comes down to earth; becoming known as Redmoon. At the same time, another creature called Erabus appears from a remote island. The Japanese government tries to bring the two monsters together so that they will kill one another. Instead, the creatures start to mate, threatening to unleash hundreds more of their kind. Fortunately, our hero Godzilla arrives in time to destroy the two beasts before they reproduce.