Saturday, the 25th of July sees the 43rd Shinjuku Eisa Festival. Eisa is a traditional dance originating in the Okinawan islands. The traditional costumes, dancing and drumming are quite different to what you’re likely to see in other festivals in Japan. The organisers are only expecting about 1 million people to turn up to watch! Mind you, this is Shinjuku so you probably won’t notice the difference.
The event runs from 12 noon until 8pm. For updates, you could check their official facebook page. It’s in Japanese, but if that’s a problem try your luck with the little ‘see translation’ link.