Akaheru

Red Helmet is one of the territories in JAPAN.

Trivia
Red Helmet is a reference to the real-world professional baseball team Hiroshima Toyo Carp (広島東洋カープ). The team was nicknamed 赤ヘル the Red Helmet during its golden era from the 70's to the late 90's (they wear red helmets).

The location of Red Helmet corrpesonds to Hiroshima Prefecture of real-world modern Japan, or the provinces of Aki (安芸国) plus Bingo (備後国) of the warring states Japan.