There is also a theory proposed by Yoshitane SAKAMOTO, Yukihisa YAMAO and others, which treated Nihon Mimana-fu as a military institution, because King Bu of Wakoku in the fifth century was awarded by the Chinese dynasty the title of King of Wa, as well as a military rank and position for six countries including Silla, Mimana and Kara, which meant that he was not recognized as a monarch but as a mere military official outside his home, the Japanese archipelago.
なお、5世紀の倭王武が倭王と新羅・任那・加羅をはじめとする六ヶ国諸軍事の封号官職爵位を得ており、中華王朝から本拠のある日本列島の外部では君主としてではなく武官の地位のみ認められていたことから、日本府の役割を将軍府即ち軍事機関と捉えた坂元義種、山尾幸久等の説もある。