According to Japanese folklore, Kaeru nyōbō are frogs that have transformed into human women to marry human men.

Kaeru nyōbō behave just like human wives, however they do not have the same strength as humans. They tend to be small and frail, and cannot do heavy jobs with their frog strength. As long as their disguise remains undiscovered, kaeru nyōbō and their human partners can potentially have many happy years together. However, there is a high risk of discovery and subsequent disaster — if a husband ever grows suspicious of his wife and happens to see her transform into frog form, the marriage will come to a tragic end.

Stories about frog brides are found all over Japan. Although the minor details vary from region to region and story to story, they often contain similar themes and follow similar patterns, such as a frog priest being struck by a rock. The following kaeru nyōbō legend comes from the folklore of Yamagata Prefecture.

Long ago an old man and his son lived together in extreme poverty. The old man often said, “Even though we’re so poor, if any woman was willing to marry my son — anybody at all — I don’t care who they are, they would be welcome!” But since they were so poor, no woman ever came.

But then one day, a strange thing happened. A young woman appeared at the door. She said, “Excuse me, but if anybody would do, would you take someone like me as a bride?”

The old man was delighted. “Come in! Come in! No woman has ever come to our home before. But I’ve always said that if anybody was willing to marry my son, anybody would do. And I think you’ll do just fine!”

The old man and his son welcomed the woman into their home. She was sopping wet from head to toe — strange, they thought, as it hadn’t rained for days. But they sat her by the fire to dry off anyway. She was extremely short — no larger than a child of three or four years. She was so small that she couldn’t do any heavy housework; although she was willing to perform any chore that was light enough for her. But the old man and his son had said that anybody would do, and they thought she was good enough.

One day, the woman needed to return to her family to attend a memorial service for her father. Although they were poor, the old man and his son scraped together a small bag of rice for her to bring to her family as a gift. They placed the sack of rice on the woman’s back, but the weight was too much for her to bear and she was squashed flat. The two men scooped rice out of the bag until it contained just 5 cupfuls, after which the bride returned to her normal shape and stood up. She was able to carry the smaller load, albeit with some difficulty. She thanked them for the gift and left the house. But the old man was suspicious of the young woman’s severe frailty. He instructed his son to follow her to see what kind of place she came from.

The woman traveled across town, then deep into the mountains. Her husband followed from a distance, and thought it very strange, as there were no homes that far up the mountain. Finally, she stopped at the edge of a marsh. She looked left, then right, and then plop! She jumped into the water. The young man rushed towards the edge of the marsh. He couldn’t see her anywhere in the dark water. He leaned in close to the water and listened. The only sound was the croaking of frogs… but they seemed to be speaking!

“What happened? How come you’re so late? We’ve been waiting a long time for you!”

“I know… It’s because I had to carry this rice! They gave me a whole bag of rice, and it squashed me flat. I couldn’t get here any faster.”

“Anyway, the priest is already here. Let’s begin the memorial service.”

The sound of frogs croaking out Buddhist prayers filled the air. The young man was repulsed. He had been tricked into marrying a frog! He picked up a rock and hurled it into the water. There was a big splash, and the croaking stopped. The man left the pond and returned home. He told his father everything.

Late that night, the woman returned to her husband’s home. “I’m sorry it took so long!” she said as she entered the house.

“How was the memorial service?” asked the old man.

“Oh wow… well it started out fine. But then a huge rock fell from the sky and hit the priest on the head — right in the middle of his prayers! It was a huge mess!”

The young man shouted at his bride. “What are you saying? You’re a frog! I saw everything! It was I who threw the rock!”

“You saw me?!” The girl was mortified. She covered her face in embarrassment. Then she transformed back into a frog and, croaking, hopped out the door. They never saw her again.

And that’s why in marriage you must never say that anybody at all will do.