Neptune’s Trident: The Sunken Realm

Neptune's Trident: The Sunken Realm is an upcoming stop motion fan fiction film that will be the seventh film in the Sailor Moon Cinematic Universe by KB Fan Fiction. The film focuses on Michiru Kaioh/Sailor Neptune.

Plot
Michiru Kaioh is on an expedition to the South China Sea off the coast of Cambodia when she discovers an unusual artefact that resembles a mirror. The site is attacked by a gang of criminals who injured Michiru, but the mirror, when held by Michiru, suddenly spews out a giant wave that washes the gang away.

The Juuban Archaeology Department approaches Michiru with information about the Deep Aqua Mirror, which is the artefact that she claimed earlier and is now in her possession. The mirror is said to originate from the lost continent of Atlantis and a supposed theft of the mirror carried out by a mysterious Youma leader of a group called the Seven Great Ocean Youma caused the continent to sink. To defeat the Seven Youma, Princess Neptune arrived at the continent to seal all of the Youma into a special crystal called the Atlantis Crystal before breaking it into seven pieces, each containing one of them. Princess Neptune later preserved Atlantis' form when it sunk.

Michiru began to see visions of Queen Serenity when she looked at the Deep Aqua Mirror. The Queen is able to communicate with Michiru with the mirror, and explains that she is chosen to be one of the "Sailor Warriors" whose job is to defend the universe from evil. Serenity also revealed that a certain Dark Agency is currently threatening the world and they must be stopped; and the mirror is needed to reactivate Atlantis, which is revealed to be a beacon built on Earth by the Moon Kingdom.

Michiru joins a special team led by Dr. Muramatsu Sanjoin to assist her in her mission to discover Atlantis. Michiru and the team head to the Atlantic Ocean, where the continent once stood. When the crew set off in a yacht to the supposed site of Atlantis from Greece, they are attacked by a swordfish Youma. Michiru defeats the Youma in a fight using the Deep Aqua Mirror's Submarine Reflection. The yacht was slightly damaged in the battle, and they had to move to Sicily to get it repaired. At the same time, another Youma, this time based on a sea turtle, attacks the boatyard. Michiru discovers that the Youma possess strange crystals, which were used to seal them inside the Atlantis Crystal during the sinking of Atlantis. Using the Deep Aqua Mirror to show the true form of the Youma, Michiru uses it to restore the Youma to its normal form while destroying the Youma side.

Later, when the expedition approaches the island of Malta, reports abound that two Youma are attacking the island, with Michiru restoring them back to their original forms: a spider crab and a manta ray. Witnessing the immense power possessed by the mirror, Dr. Sanjoin became romantically interested in Michiru.

The expedition eventually reaches the Atlantic Ocean when the yacht is attacked by a shark-based Youma, throwing Michiru and Dr. Sanjoin overboard. Michiru heals the Youma back into shark form with the Deep Aqua Mirror, while Dr. Sanjoin is kidnapped by another Youma based on a squid. Michiru chases the squid to a deep trench, where she purifies the Youma. However, she is unable to find Dr. Sanjoin. Meanwhile, Dr. Sanjoin encounters a giant being named Rahab, the leader of the Seven Great Ocean Youma. Rahab brainwashed Dr. Sanjoin and tasked him to gather the hosts of the Seven Great Ocean Youma to unite with him in an attempt to become more powerful and invade the land.

Michiru and the team has arrived at Atlantis, which is restored due to Princess Neptune's magic. At the spire, Michiru shines the Deep Aqua Mirror towards a pedestal, causing the continent to rise. The pedestal opens and reveals an aquamarine crystal, which begins to bond with Michiru. The spirit of Queen Serenity appears and reveals that Michiru had been chosen to become the Guardian of the Sea, Sailor Neptune. Realizing that the Deep Aqua Mirror possesses the power of the legendary Neptune's Trident, Sailor Neptune now has new powers, including the ability to telepathically communicate with sea creatures. At the same time, Dr. Sanjoin is about to capture the shark that became one of the Youma when the shark responded to Sailor Neptune's telepathic link and swam off.

Rahab arrives at Atlantis and begins to destroy the continent, and Sailor Neptune gathers a large army of sea creatures to battle the Great Youma. In the ensuing battle, Rahab claims the gathered fragments of the Atlantis Crystal and tries to bond with the crystal, but he is sucked into the crystal. With the battle over, Dr. Sanjoin arrives and announces his intention to take the Atlantis Crystal for himself. Michiru says to him that the crystal must be destroyed to prevent Rahab from awakening again. Michiru destroys the crystal with Deep Submerge, finally killing Rahab. Regretfully, Michiru leaves Dr. Sanjoin.

The film ends with a sunset shot of Michiru at the yacht. In a mid-credits scene, Michiru arrives in Sicily where she meets Haruka Tenou for the first time in several years.

Cast

 * Michiru Kaioh is Sailor Neptune
 * Dr. Muramatsu Sanjoin

Youma

 * Rahab, the leader of the Seven Great Ocean Youma.
 * Gwammo, one of the Seven Great Ocean Youma whose host is a swordfish.
 * Tortazard, one of the Seven Great Ocean Youma whose host is a sea turtle.
 * Ganyla, one of the Seven Great Ocean Youma whose host is a spider crab.
 * Death Manta, one of the Seven Great Ocean Youma whose host is a manta ray.
 * Cetolus, one of the Seven Great Ocean Youma whose host is a shark.
 * Krakaton, one of the Seven Great Ocean Youma whose host is a squid.

Trivia

 * The film is partially inspired by Lara Croft: Tomb Raider – The Cradle of Life and Aquaman.

References to the Sailor Moon series

 * The idea of the Seven Great Youma is the inspiration for the Seven Great Ocean Youma.