The Hyakki Yagyo, translated into English as "Night Parade of One Hundred Demons", is a massive night parade composed of a wide variety of Youkai — demons and spirits believed to be responsible for natural phenomenon of all kinds — where they party and generally cause chaos. It is often used as an idiom for riots and disorderly processions, though some believe it to be a real event in folklore. Over the years, many different interpretations of how the Parade works have cropped up.