The biggest festival and parade in the centre of Nihonbashi along Chuo Dori features over 3000 dancers and performers, most of them representing different regions of Tokyo. Also, there will be over 60 food stalls and a market where you can buy local delicacies.
Nihombashi was the starting point of Tokaido of the Edo period connecting Edo (modern-day Tokyo) to all other parts of Japan as well as the ending point of the Five Routes, thus basically the “Mile Zero” of Japan, where merchants from different regions met. This important part of Tokyo/Edo history is represented with this festival.
Many more are on the official Japanese page.
Organizer and contact (Japanese): http://nikkyo.net/
via Tokyo’s Festivals:
Tokyo’s Festivals presents an overview on Tokyo’s great festivals (mostly free festivals about food, culture, fireworks and music), so that more people find out about Tokyo’s best events. If you are interested in festivals in Tokyo, feel free to visit and like their page (Link: fb.com/TokyosFestivals) and follow their instagram (Link: instagram.com/tokyosfestivals).