Cognomen カイ (Kai , Ky , カイ ) , in all the world, is a widespread surname. The surname カイ is habitual in Malaysia, where it is a common surname, Finland, where it is quite a common surname, and Macao (explore the name in all countries). Not in comparison with a country's population, it is commonest in Malaysia, Japan, and China. Likewise, カイ is the forename as well as the last name.