Since there's only one country (Japan), all you can do in the region settings is changing your region.
AichiAkitaAomoriChibaEhimeFukuiFukuokaFukushimaGifuGunmaHiroshimaHokkaidoHyogoIbarakiIshikawaIwateKagawaKagoshimaKanagawaKochiKumamotoKyotoMieMiyagiMiyazakiNaganoNagasakiNaraNiigataOitaOkayamaOkinawaOsakaSagaSaitamaShigaShimaneShizuokaTochigiTokushimaTokyoTottoriToyamaWakayamaYamagataYamaguchiYamanashi