'Festival of the three shrines' (in Tokyo: sanja here is to be distinguished from the Ise/Kasuga/Hachiman sanja mentioned above). It is held on the three days surrounding the third Sunday in May at the Asakusa-jinja. The Asakusa area of Tokyo includes the former Yoshiwara pleasure district of Edo times. On the Saturday up to a hundred machi-mikoshi (town mikoshi) of various sizes parade through the streets and the following day the three honja mikoshi (main shrine mikoshi) called ichi-, ni- and san-no-miya make a ceremonial departure from the Asakusa jinja. The Buddhist-kami deity of Asakusa was formerly called the sanja-dai-gongen-sha 'great gongen of the three shrines' or sanja-myojin-sha 'bright kami of the three shrines' and was the tutelary deity of the area. The festival features an old style of 'binzasara' dengaku in which the dancers beat time with binzasara, wooden slats tied with cord.
A Popular Dictionary of Shinto. Brian Bocking.