Takashi YOSHIDA claims that 'Mimana' was a combination of small countries led by Mimana Gaya (Geumgwan Gaya) which cooperated with Baekje and Wa to counter Goguryeo and Silla, and thus a political concept which does not necessarily corresponds to Gaya region, and Mimana, trying to use Wakoku's military power to expand its territory, led Wakoku into establishing a diplomatic institution mainly in charge of military affairs, which was later called 'Mimana Nihon-fu'; the four prefectures of Mimana that Wakoku ceded to Baekje were the area where Wajin had immigrated.
吉田孝によると、「任那」とは、高句麗・新羅に対抗するために百済・倭国と結んだ任那加羅（金官加羅）を盟主とする小国連合であり、いわゆる地名である伽耶地域とは必ずしも一致しない政治上の概念であり、任那が倭国の軍事力を勢力拡大に利用するために倭国に設置させた軍事を主とする外交機関を後世「任那日本府」と呼んだと主張し、百済に割譲した四県は倭人が移住した地域であったという。