Translation: dragon god
Appearance: Ryūjin are powerful dragons who rule over bodies of water and serve as tutelary deities of those places. Ryūjin can refer to any dragon that is worshiped as a local kami, including major dragons such as the hachidai ryūō, Zennyō Ryūō, Kuzuryū, Seiryū, and so on. But when it is used as a proper title (i.e. Ryūjin) it most commonly refers to the dragon god of the sea—Watatsumi in Shintō tradition or Shagara Ryūō in Buddhist tradition.
Behavior: Like other dragons, ryūjin commonly make their homes in caves, rivers, lakes, and the ocean. Landforms inhabited by a local ryūjin usually have shrines dedicated to them somewhere nearby.
The dragon god of the sea Ryūjin lives in Ryūgū, a great palace made of fish scales and coral located (depending on the tradition) at the bottom of Lake Biwa, on the ocean’s floor, or across the distant horizon. He keeps a royal court full of sea creatures who serve him just as human nobles would serve a king in the surface world.
Interactions: Dragons interact with humans in similar ways to other powerful spirits. They can be benevolent kami or tyrannical monsters. They may bestow gifts upon nearby settlements when the locals please them, but when displeased they may summon rainstorms or floods to punish humans. The worst of them even demand human sacrifices or take women from their families to be their brides. The term ryūjin refers mainly to those benevolent dragons who help mankind, or those who were pacified and who promised to no longer do harm. Shrines are built in their honor, and they are worshiped as gods of agriculture and fishing, and guardians of the land.
Sea creatures act as Ryūjin’s servants and emissaries, delivering his messages to humanity—including prophecies of bumper harvests or warnings about upcoming disasters. Ryūjin’s daughters—Otohime, Toyotama hime and Tamayori hime, or Zennyo Ryūō, depending on the tradition—occasionally interact directly with humans as well.
Ryūjin sometimes lends or gives treasures to humans to help them accomplish great deeds—for example, the bottomless sack of rice given by Ryūjin to Fujiwara no Hidesato in return for slaying an ōmukade.
Perhaps the most famous of Ryūjin’s gifts are the tide-controlling jewels kanju (干珠) and manju (満珠). With these pearl-like treasures, a person can cause the tides to recede (kanju) or rise (manju) dramatically. They appear in several legends and folktales. When Ryūjin’s son in law Hoori fought his brother Hoderi, Hoori was able to use manju to nearly drown his brother and force him to submit. During the legendary 3rd century Empress Jingū’s invasion of the Korean peninsula, she used kanju to lower the ocean and strand the enemy’s ships on the sea floor. Then she used manju to raise the water and destroy the stranded fleet.
Legends: Long ago, Ryūjin’s daughter Otohime fell gravely ill. The royal doctors said that she could be cured by medicine made from the liver of a living monkey. Of all the sea creatures, only the turtle is able to climb onto the land where monkeys live. So Ryūjin sent a turtle to the surface world to bring down a living monkey.
The turtle swam to shore and soon found a monkey up in a tree. The turtle told the monkey that Ryūjin was holding a feast in Ryūgū, and the monkey was invited. The monkey replied that he had always wanted to visit Ryūgū. The turtle told the monkey to climb onto his shell, and then he carried the monkey down to the dragon palace.
At Ryūgū, the monkey was treated to a feast the likes of which he had never experienced. There was singing and dancing, and more food and sake than he could imagine. The monkey feasted and drank so heavily that soon he collapsed in a drunken haze. But the doctors reminded Ryūjin that the liver had to be extracted from a living monkey—a dead one would not do. So Ryūjin ordered his servants to take the monkey outside and sober him up.
The royal guards—a jellyfish and a flounder—carried the monkey outside to the courtyard. As they dragged the monkey’s semi-conscious body, they laughed to themselves, “What a stupid monkey! He doesn’t even know that we’re going to cut out his liver.” But the monkey was still semi-conscious, and he heard what they said. He pulled himself up onto his feet and told the guards he needed to speak to the turtle.
When the turtle arrived, the monkey told him, “Oh, turtle! I just remembered something terrible! When you found me, I was hanging my liver on a tree branch to dry. I was so excited to come to the party that I left it behind. And it looks like it might rain… If my liver gets wet it will be ruined! Please, take me back to the shore so I can get my liver.”
“If the monkey’s liver were ruined, it would be a disaster,” thought the turtle. So he quickly carried the monkey on his shell back to the shore. Once on land, the monkey climbed up into a tree and stayed there. The turtle called up to ask if he found his liver. The monkey shouted down at the turtle, “You idiot! A liver is not something you hang from a tree! I overheard the jellyfish and the flounder talking about your plan, and I will never return to the sea again!” Then the monkey started hurling rocks at the turtle. One of them chipped his shell.
The turtle retreated back to Ryūgū and reported what happened to Ryūjin. The dragon king was so angry that he cut the flounder’s body in two, and he pulled all of the bones out of the jellyfish’s body. Then he banished them from Ryūgū forever. That is why jellyfish must float about near the surface, and why flounders must lie flat on their sides.