What territory would the Aozaki Clan have?
According to a Q&amp;A with Nasu Kinoko in Fate/complete material III, the Aozaki territory that the family are administrators of, while currently unnamed, resides in Japan. 

It's mentions that these lands are the only place where True Magic can be activated and considered the greatest spiritual land in Japan. 

Mahoutsukai no Yoru reveals that this land is indeed Misaki Town. It's mentioned in Fate/complete material III that the distance between Fuyuki City and Misaki Town is equivalent to the distance of Kanto and Kyushu.