Mitake Shrine hosts a festival on the fourth Saturday and Sunday of September and is an intimate and delightful escape from central Tokyo. Located off the beaten track, it has few visitors. There are several attractive spots to relax and have some time alone. It is just ten minutes walk from Ikebukuro station, west exit.
Sanja shrine is two minutes' walk from Mitake shrine so it is worth checking out if you are in the area. This shrine is smaller than Mitake but still worth visiting, with iconic red torii gates.