At Miwagasaki in the province of Kii lived a fishing boss named Oya no Takesuke. His third son, Toyoo, was gentle by nature, loved the refinements of the capital and disliked the family trade.
One autumn day, on his way home from studying with a Shinto priest at Shingu, he was caught in a sudden shower and sheltered in a fisherman's hut, when a beautiful woman not yet twenty came in with a young girl. She said her name was Manago. Toyoo lent her his umbrella and decided to visit her house the next day to get it back.
Manago's house was a splendid mansion. "I am a widow," Manago said. "Please take me as your wife," and she gave Toyoo a precious sword. Captivated by her beauty, Toyoo promised to marry her.
But the sword had been stolen from the treasure house of the Kumano shrine. Toyoo was arrested as a thief, and when officials went to Manago's mansion, it was a ruined, abandoned house. Inside, Manago sat alone, but when the officials approached, with a sound like thunder she vanished.
Cleared of suspicion, Toyoo went to stay at his sister's house in the province of Yamato. But Manago came to visit him there. She explained herself in tears, and Toyoo let his guard down again. But when they went to see the blossoms at Yoshino, an old man named Taima no Sakato saw through her: "This is an ancient great serpent." Manago leapt into a waterfall and disappeared.
Back in Kii, Toyoo married a girl named Tomiko. But Manago's spirit possessed Tomiko and spoke reproaches to Toyoo. Toyoo sought help from the priest Hokai of Dojoji. The priest gave Toyoo a surplice steeped in the scent of poppy seeds and said, "Throw this over Manago." When Toyoo threw the surplice over her, Manago turned into a white snake about three feet long. The priest sealed the snake in an iron bowl and buried it deep in front of the main hall of Dojoji. It is said this is the "Serpent's Mound."