The Kojiki attests Yomi as the land of the dead Izanami enters. Japanese mythic geography in that court compilation, not Hades, not Duat, and not a generic underworld slogan.
The Kojiki has Izanami rule as the great kami of Yomi after her death and the underworld rupture. Yomi as realm dedicated to that sovereign, not Hel’s Norse dead-realm and not a generic underworld slogan.