Cognomen Sidai (四代 
, Sidai 
) , around the world, is a rare last name. The last name Sidai is characteristic of Kenya, where it is a rare surname, India, where it is a very rare surname, and Malaysia. Not in comparison with a country's population, it is the most numerous in India, Kenya, and China. Likewise, Sidai is the forename as well as the last name.