Akagi Castle (赤木城,Akagi Jõ?, lit. Red Tree Castle) is a castle on Hachimaru's homeworld. Controlled by practitioners of the Kongo-Yasha Style, it serves as a headquarters for Samurai and their Princesses operating in that region of the world, such as Hagamichi and Un. It also serves as a training ground and residence for young Princesses in training. Ann was a student there before leaving to travel the galaxy with Hachimaru.
Around the Akagi Castle there is a town called Castle Town (城下町,Castle Town?) that is divided in Sectors. Sector 7 (七番地区,Nanaban Chiku?) is the only know sector.