Hadaka Mairi is a "naked" pilgrimage to a temple or shrine in Japan. Actually the pilgrims wear a loincloth called fundoshi but little else. Such pilgrimages are typically done in Winter around the New Years of both the modern and old (Chinese) calendar to receive blessings such as luck and (ironically) good health for the year.
This Hadaka Mairi is part of an 800 year old ritual known as Godaison Somin done in the Tohoku region of Iwate.
https://www.youtube.com/watch?v=IaHJmmMPF4g
More info: youtube.com
