Tokyo has surprisingly many large parks in the center and Yoyogi Park is on of them. I started wondering through it from the north and there were surprisingly few people there until I arrived closer to the Meiji Shrine, which unfortunately was under renovation so could not fully enjoy it.
Before the Meiji Shrine, I also visited its gardens.
In Japan, before you enter a temple, you typical wash your hands. Some of them also offer the option of attaching your wishes as they did at Meiji shrine.