Kumagawa Shrine is a sacred site where the spiritually minded come together to pray. You can do the same, or respectfully observe others as they worship.
You'll have sightseeing choices galore when visiting Fussa. Kumagawa Shrine is an ideal place to start here, but there are many other fine sights to check out. Belluna Dome, Shinnyo-en Head Temple, and Tokyo Summerland are not far from the sacred place and will round out your day nicely.