In 1933 New York, an overly ambitious movie producer coerces his cast and hired ship crew to travel to mysterious Skull Island, where they encounter Kong, a giant ape who is immediately smitten with the leading lady.
French nuclear tests irradiate an iguana into a giant monster that viciously attacks freighter ships in the Pacific Ocean. A team of experts, including Niko Tatopoulos, conclude that the oversized reptile is the culprit. Before long, the giant lizard is loose in Manhattan as the US military races to destroy the monster before it reproduces and it's spawn takes over the world.
The film consists of re-edited material from the original television series Ultraman. Episodes 1, 8, 26, and 27 were used for the film. They were narrated by Hikari Urano as an "Ultraman Documentary". Allegedly only one new scene was shot, and that some parts of the movie where shot in black and white for unknown reasons. The movie screened at the same time as the Toho movie King Kong Escapes.
The U.N.G.C.C. (United Nations Godzilla Countermeasure Center) recovers the remains of Mecha-King Ghidorah and construct Mechagodzilla as a countermeasure against Godzilla. Meanwhile, a giant egg is discovered along with a new monster called Rodan. The egg is soon found to be none other than an infant Godzillasaurus.
A special retrospective of the two franchises, with segments making comparisons between the different characters, their weapons, powers and so forth. The final segment of the special is the short film "Super Battle: Ultraman vs Kamen Rider" The main characters, Ultraman and Kamen Rider 1 appear on the scene separately, each fighting an original kaijin and kaiju. When the two monsters are nearly defeated, they merge into a more powerful kaiju. Ultraman experiences trouble and calls for Kamen Rider 1's help. Kamen Rider 1 is then able to grow to enormous size to fight alongside Ultraman.
A ghost mage that can manipulate the soul of any monster appears, with the intent of ruling the universe. With a new enemy that can manipulate a monster's soul, Ultraman Orb and Ultraman Zero emerge to stand in his way. Orb will fight a ghostly villain with ghost monster army corps through various fusion ups including Lightning Attacker with the power of Ginga and X! Orb will fulfill new fusion ups while the mighty warriors of the lights appear to assist Ultraman Orb. Even with Ultraman Orb's new forms, will he be able to overcome the threat of Reibatos?
An expedition in the South Pacific lands on a tropical island where the natives worship the mysterious deity Gappa. An earthquake opens up an underground cavern and a baby reptile is discovered inside. The natives warn the foreigners to leave the hatching alone, but they don't listen and take it back to a zoo in Japan. Soon after, moma and papa Gappa start smashing Tokyo looking for their kidnapped child.
The advertising director of Pacific Pharmaceuticals, frustrated with the low ratings of their sponsored TV program, seeks a more sensationalist approach. He orders his staff to Faro Island to capture King Kong for exploitation. As Godzilla re-emerges, a media frenzy generates with Pacific looking to capitalize off of the ultimate battle.
Journalists Ichiro Sakai and Junko cover the wreckage of a typhoon when an enormous egg is found and claimed by greedy entrepreneurs. Mothra's fairies arrive and are aided by the journalists in a plea for its return. As their requests are denied, Godzilla arises near Nagoya and the people of Infant Island must decide if they are willing to answer Japan's own pleas for help.
At the turn of the century, all of the Earth's monsters have been rounded up and kept safely on Monsterland. Chaos erupts when a race of she-aliens known as the Kilaaks unleash the monsters across the world.