Yōkai are creature in old Japanese stories, such as oni, kappa, or tengu. They have mysterious supernatural powers. There are thousands of yōkai. In the Edo period, yōkai were characters in story books. Recently, many new yōkai have been made. There is even a yōkai dictionary. The yōkai are monsters or ghosts in Japanese tradition. In the past people believed they caused disease, accidents, and natural disasters. People were often scared of them.