Surname Nagai (ナガイ , Nagai , 永井 , along with others...) , around the globe, is quite a common cognomen. The surname Nagai is characteristic of Ghana, where it is quite a rare surname, Ukraine, and Japan. Not in comparison with a country's population, it most frequently occurs in Japan, Brazil, and Ukraine. More frequently, Nagai is the forename as well as the last name.