I have revised this research on Mimana-no-cho(任那의 調). The results are as follows.
Mimana-no-cho is basically a foreign policy of Wa(倭王權), so it has to be understood as Shilla(新羅) Foreign Policy.
I checked the several reasons to assert these findings. The origin of Minaman-no-cho Policy was made as Shilla Foreign Policy by the Wa's regime of Bitatu(敏達朝). Its historical background originated the fact that Kaya(加耶)'s territory, especially Keumgwan(金官國) and Alla(安羅國) located in Southern part of Kaya played a significant role, was the biggest source of import and supply of meterial resource, including iron for Wa's regime. Therefore, Mimana(任那) of Mimana-no-cho doesn't mean the only one country of Keumgwan(金官國). The essence of Mimana-no-cho was the practical and active foreign policy to import an abandunce of material resource for the domestic demand in Wa through Shilla.
The minama-no-cho was originated as a result of Wa having filled up on its domestic demand of material resources -- including gold, silver, and bronze -- through the exchange with Kaya before Kaya went out of existence. Wa coped with the domestic demand of material resource through the exchange until sometime during the 560th.
I assert the essence of Wa's regime's Mimana-no-cho's policy was to meet the need of material resource through the exchange of material resources with Shilla instead of Wa after Wa lost Kaya which was the biggest source of supply of material resource, during the 570's.
In addition, Mimana-no-cho was Shilla Foreign Policy to deal with the domestic need of material resource, at the same time it was probably the first National Policy to get material resource for Wa's regime Bitatu(敏達朝) during the 570th.