Kumano Shrine currently reduced to the far corner of Shinjuku Central Park is one of the oldest shrines in Tokyo often picked by Ukiyoe wooden block paintings. Annual festival which is simply called "REITAISAI" is held in mid to late September. This year(2013) the festival will be held on September 21 to 22.
To see the festival of 2012 see this youtube link.(In Japanese)
There are about 1,300 shrines which enshrine Konohana-Sakuyahime, the goddess which has been believed to reside in Mount Fuji. Some of them are called ASAMA shrines and others SENGEN, but both share the same Chinese Characters. Fujinomiya Sengen Taisha Shrine at the southwest foot of Mount Fuji is the head shrine of all the Asama/Sengen shrines in Japan. Sengen shrines in and around Tokyo often have some mounds or natural hills nearby with the name fuji affixed. These mounds are called Fujizuka. There are about 100 fujizukas in Tokyo alone but some are lost because of urban development and the only monuments remain. Geino Asama Shrine at the far corner of Hanazono Shrine near Kabuki-cho area also has a small fujizuka mound only about 1.5 meters in height. It is called Shinjuku Fuji.
Reitaisai(Annual Festival) of Kumano Shrine
September 21-22, 2013
Tori-no-Ichi of Hanazono Shrine
November 2-3, November 14-15, November 26-27