Kurokaijū (ku.ɾo.kaɪ.d͡ʑɯː)

"The first I noticed was that the boat stopped moving. The wind died, and the air was cold and too still. The lamps went dim, and the sky was a blank grey expanse of clouds.

Then I saw it. It was looming over the ship, a dark shape so large that it had to lean down to touch our mast. I couldn't breathe. I couldn't move, or speak. I stood gripped by terror unlike anything I had experienced in two decades of military service.

The creature stretched out a hand towards the ship. It passed through the masts, and the sailors between the hand and the deck, but not the deck itself. It pressed down like our ship was a toy, pressing us down into the ocean. I could see as water began to spill onto the deck, but then a sharp crack broke the silence. Hua Renxi had lit her firecrackers, and the shadow recoiled from the noise. The spell of silent terror broke, and I yelled and shouted and stamped my feet. The other sailors did the same, those who were still made of flesh. The sounds repelled the great shadow, and it vanished back into the night and the sea. I hope to never encounter its like again." - Minato Ōgami, Kaiyō Taishō of the Wamatoan Navy

The Kurokaijū is a kind of Yokai sometimes seen in the Northwestern Region, most often in the area around the Empire of Wamato. It manifests as an enormous shadowy figure standing waist-deep in the ocean, looming over any ships in the vicinity. When the Kurokaijū appears, the sea and wind grow unnaturally calm and still, and the lights grow dim and weak. People who see the shadow are usually frozen in terror, unable to move or fight as it approaches the ship, reaching out a vast hand to push the vessel underwater. It can choose when to be solid and when to be insubstantial shadow, passing through ship and sailor alike.

The Shadow of Death

Those who are enveloped in the shadow of the Kurokaijū are slain by the encounter, and their flesh transformed. Their bodies become a soft and crumbly stone that is easily shattered and turns into dust over a few days. This dust resembles ashes more than anything else, and it is as if they were rapidly cremated, but without flame or heat. Some stories tell of captains who attempted to ram a Kurokaijū, only to slide right through its body and kill everyone on board.

A Noisy Defense

For those who can shake off the terror induced by the Kurokaijū, the best defense against them is noise. The vast yokai cannot bear loud noises, and will retreat if the crew can raise enough of a clamor. Since the introduction of firecrackers on Wamatoan naval vessels, they have been used a few encounters with the yokai, to great effect. But there are also cases where the ship was lost despite having firecrackers, presumably because nobody on board could move enough to light them before the vessel sank.

Firecrackers in Wamato

For generations, Wamatoan travelers have placed bamboo stalks into their campfires, so that they would explode with a large pop and frighten away predators. In recent years, this ancient defense has been augemented by the invention of Huǒyào, or 'fire powder'. This substance explodes much more violently when burned, and has been used fill bamboo stalks and make firecrackers that create a huge flash and sound. The Wamatoan Navy has adopted them for use in ship to ship communications, and they have also proven very effective at driving away certain kinds of Yokai.

The Kami and the Yokai

In the Empire of Wamato, theologians have long debated the exact difference between Kami and Yokai. Both are Numina, born of the beliefs and ideas of the people of the empire, but their relationship with those people is profoundly different. While it is tempting to place them opposite each other on a spectrum of good versus evil, this is too simplistic a model to describe the truth. There are some Kami who are malevolent and use fear to drive their worship, while stories will occasionally tell of Yokai who perform great acts of kindness and charity. In the end, it appears that the main difference roots with how the Empire classifies the spirit, and how that impacts the relationship of the Yanjin people to the Numina. Kami are given shrines and worship, while any worship of the Yokai is crime against the Emperor, punishable by death. This impacts how the people think of each group, pushing each group towards the mold assigned to them by the priests and the Emperor. You can read more about Numina and how they are shaped by belief here.