It’s not so famous, but I the Shinagawa Matsuri is one of the best festivals I’ve seen in Tokyo. There’s a procession of people in costume from the Edo Period (1609-1867), and then a firewalking by priests and spectators. The procession of people in historiecal costumes is similar to Asakusa’s Jidai Matsuri on November 3, but the Shinagawa version is a little smaller, so it’s not nearly so crowded, and there’s a lot more of a community feeling to it.
The first part of the fire festival is really intense. The priests all stand around chanting, and sometimes one of them will put a wet branch into the fire and flagellate themselves with it. Then they take turns running through the fire. After that, the fire is put out, and everyone is invited to walk over the hot coals, so if you’ve ever wanted to try firewalking, this is your chance.
The procession before the firewalking ritual includes contestants from the Miss Shinagawa contest, as well as samurai, courtesans, ninja, and characters from history. Some of the costumes are pretty cheesy, but there are lots of good ones too.
The Shinagawa Matsuri is held on the last weekend in September. The procession and firewalking are on Sunday and start from around noon. Here’s a link to the festival’s website (Japanese only): http://www.shinagawa-syukuba.com/