Last name せいじ (Seiji 
, せいじ) , in the entire world, is quite a rare family name. The family name せいじ is characteristic of Japan, where it is quite a rare surname, Taiwan, where it is a rare surname, and Singapore. Measured by absolute frequency, it is the most numerous in Eastern Asia, particularly Japan, China, and Taiwan. Likewise, せいじ is the forename as well as the last name.