Among the top top top souvenirs is
in Koenji, every August (this year from 12th 15th in Tokushima and end August in Koenji), a million of people gather in the street to see over 2000 dancers completing the Awa Odori dance. This is a o-bon dance, plenty of classes teach you and nowadays you can see Westerners dancing during the fair.
Make sure you cope with the crowds as it is absolutely packed but the atmosphere is truly family style, friendly, and the more you stay, the more you get into the vibes, it is almost transcendental, you get into it!!
Go for it. this dance dates back from the middle age in a southern city in Shikoku (Tokushima). You will see the woman dance, the men dance. extraordinary!!
It is a brilliant day out, enjoy the music, the atmosphere, sit in the cafes around for yakitori and beer evening. It was a must in my calendar, something I would never miss, and I even planned my holidays around it to make sure I would be here!!