Incidentally, the word "Kanto" in this case indicates the Kamakura bakufu itself rather than the location of the provinces, (today, "Kanto" specifies the central-eastern region of Japan including Tokyo, and Kamakura, where the bakufu was also established) therefore Kanto Gobunkoku meant not just the provinces located in the eastern region, but also the provinces located in the western part of Japan under the ruling of the Kamakura bakufu.
なお、ここで言う関東とは鎌倉幕府の所有という意味で、東国のという意味ではなく、西日本にも数多くあった。