The Story of the Dragon-King's Daughter: my summary of a Chinese Folk Tale
A failed student, Liu Yi, was returning home when he encountered a poor shepherdess with a flock of aloof-looking sheep. She told him how she was really the Dragon-King's daughter, and had been mistreated by her husband, and left to look after his sheep in the rain and the wind. She asked him to convey a message for her to her father who lived under Dong-Ting lake, but first he had to swear he would not betray her. After he had sworn on his life, she told him that he had to go to a sacred orange tree south of the lake, change his belt for the one she gave him and knock on the tree three time.
After a month he managed to go to the tree and did as she said. This summoned a warrior came who parted the lake and led him to a splendid palace (decorated in the usual precious stones, silks and other fabulous flourishes). The king (who was dressed in purple but otherwise human looking) was in consultation with a human priest. The king was in charge of flooding, whereas the priest in charge of fire, and so they trying to reach a compromise. When they had finished, Liu Yi spoke to the Dragon-King and passed on his daughter's message. The king was grateful. Presently, the king's brother, a red dragon, who had been imprisoned by overlords at the Jade Palace for anger management issues, arrived with lots of women including the king's daughter. It turned out the king's brother had already rescued the daughter after killing thousands of people in battle. The errant husband of the Dragon-King's daughter had made a tasty snack. The king reproached him for this, but since his brother had obviously been forgiven for this crime and previous ones by the Jade Palace he decided to let it pass. Much feasting and rejoicing occurred.
The king's brother then threatened Liu Yi and told him that since the king's daughter was now widowed , she's make a good wife, so he had better marry her. Liu Yi said he didn't care how big the king's brother was, he was not going to be bullied in to doing anything. However, when it came to saying good bye to the Dragon-King's daughter, Liu Yi realised he had made a mistake, but it was too late then.
He went back to dry land and the world of men, made a fortune with the gifts he had been given from the Dragon-King and his brother, married and subsequently widowed twice in succession. He was then approached by a matchmaker who proposed that he married a widow who was still young and desirable. He agreed. After they had had their first child, the widow revealed herself to be the Dragon-King's daughter in front of everyone. She then confessed that her normal life-span, as a dragon, was likely to be ten thousand years, but she would share these years between them. For many years they lived very happily as humans, but then they were bothered by Emperor Kai Yuan (AD 713- 741) who was after the secret of longevity. So to elude him they lived thereafter under Dong-Ting Lake - which really exists, so it must be true.