Prologue-
The eastern Pacific Ocean; a beautiful expanse of glittering blue saline topped with the white crests on the rolling brine. The sun shone down on the white sands of the western coast of Honshu's Sagami Bay, 1528. Overhead, shearwaters and kamchatka gulls circled over the churning ocean, searching for fish near to the surface to be snatched up and carried off to their nestlings squatting on the cliffs by the coast. Above the water, the beauty was pristine and vast, but below the water, the tempered flow from the Kuroshio Current kept the waters naturally warm year round and lead to vast biodiversity in the region. Creatures of all shapes and colors navigated the rich waters of that bay; creatures that have long since died off or disappeared into the vastness of mythological history. You may write it all off as legends passed down and losing their grip on reality with every generation, but in truth, the 14th century was home to many great, powerful and noble creatures.
The land back then was thick with demon life; the forests running wild with plentiful game and unnaturally powerful beasts and men. The seas of the era were chock full of elegant aquatic life, but also were home to ocean-faring reptilian monsters like from old epics. Still with all the pristine majesty and raw power that pulsed from the earth in the ancient times, no creature was more magnificent than the ningyo, merfolk to the modern world. The ningyo were creatures with the upper bodies of men and women and the tails of fish native to the region and commonly dorsal fins that stretched the lengths of their spines. Many were plain, though marvelous in their own right, most commonly resembling the sea bass, green in color and generally spiny in the dorsal region. Some were vicious having the characteristics and lower body appearance of dogfish, scorpionfish and even sharks. Still others where more wondrous than the rest, with long swooping dorsal fins, colorful scales and flowing tails that were the envy of the sea.
Many fishermen of the time would be visited by the ningyo, especially the further out their boats sailed. It was not uncommon for a crew to return missing a member who had dove overboard after a maiden of the bay, earning the more elegant women the name "siren." Unlike the stories that have been stretched to this day, the sirens did not have the ability to coax men overboard with their lovely singing. Though singing was a vast part of the ningyo's culture, they were completely aquatic, their voices being only able to sound correctly under the surface. Above the water, if a merwoman were to attempt to serenade the crew of a passing vessel, her voice would screech and moan and be more likely to drive them overboard if only to escape the sound of her wails. All the same, sometimes the beautiful creatures were captured in fishing nets and hauled aboard, screeching and howling like banshees, only for them to suffocate for lack of water reaching the fan-like gills on the sides of their throats.
Many, many rumors and stories surrounded the ningyo in the society of men. There were fables passed for countless generations of the magical properties held by the 'human-faced-fish.' The most famous tale was of a fisherman who happened to capture one and invite his friends to supper where the creature was roasted and passed around. Having seen the humanoid part of the ningyo's body, one of the men at the table warned his fellows not to eat the fish they were served. Instead the men all wrapped the meat in paper to be discarded later. However, one of the gentlemen after having drunken a bit too much sake, absently gave a piece of the merfolk's flesh to his daughter who then lived on as a young woman for over eight hundred years.
Legends also tell that the ningyo would cause great storms if captured, and that one washed ashore was an omen of war or other catastrophe. Though over the course of many years, fewer and fewer land-dwellers believed in the stories of old, accepting the gentile water creatures as simply another breed of fish in the bay. As such, the ningyo were left in privacy for the most part; there was hardly a fisherman at the time who could stomach eating a creature which was half human. Though no official laws were ever written while the merfolk still survived, it became a social taboo to hunt the beings as game.
Though the ningyo did not create formal societies, they did tend to form close-knit groups, known as pods, similar to the migrating proposes. They tended to make their homes in coral reefs and kelp beds instead of building vast, underwater kingdoms as many legends may claim. The simple fact remained that they were a culture of aquatic, social nomads.
There were many pods of merfolk that made their home in the warm waters of the Sagami Bay; there were the Kobushichi, the Kinkyoha and the Akatsuki. Of course every clan has its own stories, and even every ningyo, but this story focuses on one in particular; a male, member of the Akatsuki, named Deidara, and how he fell in love with a half demon.