Last name Kosei (Kosei 
, コウセイ , Косей 
) , in the entire world, is a common cognomen. The surname Kosei is characteristic of Japan, where it is quite a rare surname, Ukraine, where it is a rare surname, and Hungary. Not in comparison with a country's population, it most frequently occurs in Japan, Ukraine, and China. Very seldom, Kosei is the forename as well as the last name.