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The Karuta Realm (or officially known as the Kingdom of Karuta and simplified as Karuta) is the well known realm of Battle Day Zero and a recurring setting for the series of Exchange Student Zero.


Karuta is controlled by its king as an absolute monarch, under the system of imperial autocracy.

Foreign relations

Karuta was one of the major kingdoms who participated during the war for power of Battle Day Zero that ended with a truce. It maintains its alliance with the Canillian Principality and is constantly at war with other kingdoms, most notably the Kingdom of Blackyard.


  • The realm of Karuta shares the same name as the Japanese competitive card game, Karuta.