On May 5, 2012, 100,000 blue LED spheres floated down the Sumida River in central Tokyo to kick off the inaugural two days Tokyo Hotaru Festival. The LED’s dubbed prayer stars were provided by Panasonic, who stated the spheres were 100% solar-powered and designed to be large enough so they wouldn’t be swallowed by fish.
The LEDs are meant to resemble Hotaru (fireflies) as they float gently down the river. Onlookers gathered on the river’s edge to take in the surreal event. Japanese design blog Spoon & Tamago were the first to cover this, stating that there are many literary references regarding the Sumida River once being a haven for fireflies.