Cognomen Касаи (Kasai 
, 川西 
, 香西 ) , all over the world, is quite a common family name. The last name Касаи is characteristic of Nepal, where it is quite a rare surname, Israel, and Hong Kong, where it is a rare surname. Measured by absolute frequency, it most frequently occurs in India, Nepal, and Nigeria. Also, Касаи is the forename as well as the last name.