MIZUNO supposed that in the 6th and 7th century, there was a ruling system in which the country was not reigned by only one Okimi (great king) but was ruled by a group of rulers including Okimi, based on the division of domains, and that Emperor Tenchi tried to change such a function of Okimi (emperor).
水野は、6、7世紀には大王一人が君臨する体制ではなく、大王を含めた支配グループが共同あるいは分業で統治する体制があったと想定し、天智天皇はこのような大王（天皇）のあり方を変えようとしたのだと考えた。