Bon Odori festivals are traditional events that celebrate ancestral spirits with dancing, and they're typically held in the summer months. If you're visiting outside that timeframe, there's a bon odori event happening in Tokyo's Tachikawa area in October which is bound to be plenty of fun.
The Tachikawa Yokai Bon Odori will run for three days, and is set to include dancing, a yokai (supernatural spirit) costume competition, various live music and DJ performances, and festival stalls.

Admission to the event itself is free, but some areas (such as the paid stage area) have fees associated with them.