Youkai are a class of supernatural creatures in Japanese folklore, often depicted as spirits or monsters. They can take various forms, ranging from friendly to malevolent, and are known for their unique characteristics and abilities. Some well-known types of youkai include Kappa, which are water-dwelling creatures, and Tengu, bird-like beings associated with mountains. These entities play a significant role in Japanese culture, influencing art, literature, and festivals. Youkai are often featured in traditional stories and modern media, such as anime and manga, where they continue to captivate audiences with their mysterious and diverse nature.