Intended Release: 1990
Mothra vs. Bagan
[Mosura vs. Bagan]
A large avalanche occurs in the Himalayas, awakening the legendary monster Bagan and sending it on a wave of destruction.
Meanwhile, while monitoring the deforestation status in China using the Landsat, Global Environment Conference staff member Masako Tezuka discovers a strange object in the depths of Borneo Island. Together with TV director Kenji Andoh, photographer Takuya Fujita, and two of the locals Jouji Minamigaki and Puto, Masako and the other four meet up at the designated location and find a giant egg accompanied by two small beautiful fairies, the Shobijin. However, Minamigaki concocts a selfish plot to kidnap the Shobijin to take with him to Japan as souvenirs, and he succeeds. While Masako and company track Minamigaki, the giant egg hatches, and Mothra Larva is born.
Mothra Larva pursues the fairies and appears in Singapore, preventing Minamigaki from escaping to Japan. The larva ends up fighting with and temporarily repelling the nation's army but is seriously weakened, and she cocoons herself against the Westin Stanford Hotel. The army takes this opportunity to counterattack using four heat masers, but this strategy ends up having the opposite effect as the larva's metamorphosis is sped up, and the adult form of Mothra emerges from the cocoon.
After easily dispatching the masers, Mothra resumes her pursuit of Minamigaki, who at the time is on a train headed to Bangkok while being confronted by Masako and company. Suddenly, Bagan appears, and Minamigaki is killed amidst the fierce fight between the demon beast and Mothra. When Bagan vanishes into the sea, Andoh secretly snatches the Shobijin and heads to Bangkok with the others.
Mothra is once again attacked by the nation's Armed Forces, this time in the sky, but the agitated goddess outmaneuvers and destroys the aerial fleet. She then appears in the skies of Bangkok, but by this time Masako, now accompanied by Miki Saegusa, who was hired to track Bagan but ended up hearing the S.O.S. call of the Shobijin in the process, retrieve the fairies successfully and quell Mothra's anger.
Masako and company take the Shobijin to the Royal Racecourse to meet up with Mothra. The Shobijin use their language transformation abilities to communicate, and explain the history of Mothra and Bagan: "Mothra was the forest-protecting god from long ago, and Bagan was the god of darkness. In an ancient battle, Bagan was sealed away in the Himalayan Mountains, but the monster has been revived due to recent deforestation."
Before the Shobijin and Mothra can depart, Bagan launches a surprise attack from the sky, and Mothra is gravely injured in their battle. Seeing the weakened adult's plight, the Shobijin sing their song, giving birth to a new Mothra Larva from a giant egg in the depths of Borneo Island. Weakening Bagan enough with her poison powder, Mothra takes Bagan to an island and is accompanied by the newborn Mothra Larva, who rushes to the battlefield. Fighting with their lives on the line, the combined powers of the larva's web attack and the adult Mothra's poison powder finally defeats Bagan. Everyone cheers. The adult Mothra then carries Bagan's wrapped body out to sea, where with the last of her power she seals the demon in the depths of the ocean. Soon after, Mothra's dead body dances down from the sky.
Before leaving with Mothra Larva, in their final wish to everyone, the Shobijin plead: "Please do not awaken Bagan again. Mothra bet her life and confined it in the sea. Please, do not waste Mothra's death." Masako and company see the new Mothra and the fairies off, promising to do their best to better the world. Boarding helicopters, they find the adult Mothra's floating body, her shiny wings spread out on the ocean's surface, drifting away on the waves...
Deep beneath the Pacific Ocean, something begins to stir. The violent battle between Mothra and Bagan influenced the condition of a sleeping beast, restoring it to full health. The world would soon be at the mercy of a familiar threat: Godzilla.