This legendary creature is composed of lightning. Its name means thunder animal or thunder beast. It is the companion of Raijin, the Shinto god of lightning, thunder, and storms who looks like a demon and pounds his drums to create thunder. Raijū can take the form of a wolf, a dog, a fox, a cat, or a weasel. It is most commonly depicted as a white and blue wolf or dog. Raijū can fly around in the form of a ball of lightning. Its cry sounds like thunder.

Raijū is normally calm and harmless, but it becomes agitated during thunderstorms. During thunderstorms, it leaps through trees, fields, and buildings. Trees that have been struck by lightning are said to have been scratched by Raijū's claws.

Raijū has a strange habit of sleeping in people's navels during storms. Some say that he only sleeps in the navels of people who are sleeping outside. Raijin shoots lightning arrows at Raijū to wake it up when this happens, harming the person Raijū is sleeping in.

FUN FACT: To avoid having Raijū sleep in their navels, superstitious people sleep on their stomachs during bad weather.

Examples in various media:

Thunder (Cardcaptor Sakura)

Raikou (Pokémon) Manectric is another example.

Mukou (Touhou Ibarakasen ~ Wild and Horned Hermit)