It is presumed that Soonoiwaki meant Kokubu-jo Castle (Osumi Province) and Shimizu-jo Castle and Himenoki meant Himeki-jo Castle and Tachibanaki-jo Castle, while there are conflicting theories concerning other five castles: one claiming that the castles were concentrated near the Kokubu Plain and the other claiming that they were widely dispersed in southern Kyushu.
このうち曽於乃石城は国分城(大隅国)と清水城、比売之城は姫木城と橘木城であったと考えられているが、他の5城については国分平野付近に集中していたとする説と九州南部に広く分散していたとする説がある。