Mud-throwing festivals. A variant of hadaka matsuri, winter rites for purification and good harvest in which participants strip down and wrestle, covering each other in mud, wet ashes or charcoal. At the Dairokuten-no-hadaka matsuri at the Musubi jinja, Chiba on February 25th, fundoshi-clad youths make their way from the shrine to a nearby lake and return covered in mud, while at the doronko matsuri of the Katori jinja on April 3rd, also in Chiba, youths married during the year cover themselves with mud and carry mikoshi.
A Popular Dictionary of Shinto. Brian Bocking.