Insular Japan, sometimes called Greater Yamato, refers to that part of the Japanese Empire which consists of Yamato, Lùquiù and Ezo, that is, excluding Corea. These three constituents share a common heritage and language, and often form an informal union. The division between Corea and Insular Japan is recognized in, for example, Battlegame, in which Japan has two national teams, Corea and Insular Japan.
The term was first used (at the time as a synonym of Yamato) after Corea's assimilation into the Empire, and became more common after Lùquiù joined the Empire.
Some politicians have proposed restructuring the Empire into a two-part federation of "Japan" (Insular Japan) and Corea, to be renamed the Nissen Empire.