Some of my friends have joined Sanja Matsuri(festival) many times.
One of my female friend told me that it’s usual to see somebody are fighting each other and she could see people with Japanese style tattoo(Irezumi) during the festival.
But now the people with tattoo have to hide their tattoo they can join the festival.
Nowadays in Japan,there are some strict rules about tattoo in public places aside from this festival.

Source of a Quote Wikipedia SANJA MATSURI(三社祭)

SANJA MATSURI, which is one of the Three Great Festivals of EDO (now Tokyo), is held on the third Saturday and Sunday every May by the Ujiko (inhabitants of the neighbouring community) at Asakusa Shrine (previously called “SANJA Daigongen Shrine”),sacred to the tutelary deity of the locality ,Asakusa. Although the festival seems to date from older times, the presentday from of the festival was established in the Edo period (1603-1868). The parade of the portable shrines is conducted primarily for the mutual amity of the Ujiko and he prosperity of the community but also enjoyed by people other than the Ujiko.
Source of a Quote ASAKUSA SHRINE

The Three Great Festivals of EDO are “Kanda Matsuri(神田祭)” “Sanja Matsuri(三社祭)” “Sannou Matsuri(山王祭)”.

Source of a Quote Wikipedia SANJA MATSURI(三社祭)

Asakusa Japan SanjaMatsuri Daigyouretsu 2014

Sanja Matsuri ・In front of the shrine・Fight・Magnificent・An angry roar 2015/05/17