Japanese yo-yos are colorful water balloons with an elastic string tied around it so that you can bounce them up and down like a yo-yo. They're very popular at matsuri in Japan and can be found sometimes at Japanese-style festivals and carnivals here in the U.S.

I don't know what they're called in Japanese and my attempts to look it up online proved fruitless. If anyone knows what they're called, please comment and let me know.

This photo was taken at the Natsu Matsuri outdoor event at the Mitsuwa Marketplace in Torrance, California on July 22, 2007. Mitsuwa is a chain of Japanese markets. The Torrance store especially seems to cater to the workers from the local major Japanese businesses (Toyota, Honda, etc) and others from Japan.

Mitsuwa Marketplace
21515 South Western Ave
Torrance, CA 90501
310.782.0335