Yōkai are a type of creatures appeared in Japanese old stories, such as oni (the evil), kappa, or tengu. There are thousands of yōkai. In the Edo period, yōkais are used as character of stories in books, and in this age many new yōkais are made. Even yōkai dictionary was made. The yōkai are monsters or ghosts in Japanese tradition . They have mysterious power. In the past people believed they cause disease, accident and natural disaster. In the past, people believed in yōkai, and often scared of them.The most famous yōkai are Tengu, Oni (Japanese ogre), and Kyubi no Kitsune (a fox with nine tails). When some people and animals have strong hate, they became yōkai, for example, Sutoku. Sutoku (Japanese ancient emperor) died with strong hate. Then, he became Tengu and caused disaster. Besides the cat which lived too long time became Nekomata. Recently, yōkai are familiar with people as subculture in Japan.