Koro Koro is a Japanese onomatopoeic expression for the sound of something spherical, fat or small “rolling” or “tumbling.”

The expression is often associated with this Japanese fable about an old couple and the fortunes they reap by sharing their rice balls!

The Old Man and the Rice Ball

There was an old couple who lived in the mountains. One day, when the husband set out to fetch some firewood, he stopped to eat the rice balls his wife always packed him for lunch. While he was eating, one rice ball fell on the ground and koro-koro rolled down the mountain, into a hole. When the man approached the hole he heard singing. “Rice Ball Koro Koro, Rice Ball Koro Koro.” Curious about this unusual song, he tried to throw another rice ball in the hole, when he lost his balance and fell in. On the way down he heard more singing. “Old Man Koro Koro, Old Man Koro Koro.” He had fallen into a mysterious underground world of mice. He stayed for a while to eat, sing and dance with the mice and when it was time for him to leave, they presented him with a box for kindly having shared his rice balls! When the old man arrived home, he and his wife opened the box to find it filled with gold! Enough to last them the rest of their days.

When the old couple’s greedy neighbor heard of their story, he decided to try and get some gold for himself. He found the hole and threw a rice ball in. He heard the same singing “Rice Ball Koro Koro, Rice Ball Koro Koro.” He jumped in the hole and saw all the mice and the same box his neighbor had received. To scare the mice away from the gold, the neighbor pretended to be a cat crying “meow meow!” Suddenly, the hole went dark and everything disappeared! There were no mice and there was no box of gold and there was not even a single rice ball left for the old neighbor to eat!

Since that time, no one has ever found the mouse world again.
Although sometimes, if you are walking high up in the mountains of Japan, you may hear this song carried by the wind…“Rice Ball Koro Koro, Rice Ball Koro Koro.”