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Dahan (Japanese: だいかん, Chinese: 大漢) is a portion of the southern half of China that quickly after the start of World War III was able to break away and establish itself as an independent nation apart from the Great Asian Union. 
Due in part from the Great Asian Union which dominated the northern part of China and the Korean peninsula since AD 2060, Japan and Dahan although not formal allies shared a common enemy and cooperated militarily. 
After Asia split into North and South, the Kunlunfang Institute attached itself to Dahan when it became an independent country, thus causing the Great Asian Union to lose almost all of its expertise in Modern Magic. This allowed Dahan to stand toe to toe with the Great Asian Union despite its inferior resources. It could be said that the Kunlunfang Institute was the nucleus of Dahan's military strength. 
In April of AD 2062 during the cultural exchange program, while in Taipei, Yotsuba Maya was abducted and Saegusa Kouichi suffered injuries from assailants linked to the Kunlunfang Institute of Dahan. Subsequently Maya was raped and experimented on.  Dahan internally collapsed in February of AD 2064 (1½ years) after the Yotsuba retaliated against Dahan.  This allowed for the Great Asian Union to absorb Dahan. 
Due to the war between the Yotsuba and Dahan, approximately four thousand: cabinet ministers, high class bureaucrats, officers, magicians and researchers were all assassinated.  The Great Asian Union doesn't offer any protection or resources to those who are from Dahan, in fact they demand that they be provided with resources, and thus they've forced people from Dahan to work for the Great Asian Union.