This will be a brief post in which I won't discuss any particular of Amino's works. Instead I would like to suggest an interpretation of the relatively early works discussed so far taken as a whole.
Look at his talk of clubs (saibô), stones, river banks, goblins, muen and the "primitive". Look on the other hand at how consistently he focuses on the potential of these things to limit and resist secular power. The conclusion, to me, is clear. Amino's central concern in the works discussed so far is the opposition between the sacred and power, or, more precisely, the ability of "sacred things" - things that appear to transcend human power or understanding - to relativize and destabilize the logic of secular power, the logic of "interest" or the "strategic rationality" that rises to preeminence in the age of money and military might, which is also our modern world.
The importance of bringing in the "sacred" as a potent social force is immense. A society in which the sense of the sacred is strong will follow different laws - a different logic - than the one in which secular interests rule. This insight can be of great help in sociology. It helps us see that "strategic rationality" is limited not only by what Habermas calls the "communicative rationality" of people engaging in rational discussions, but also by lingering vestiges of the sacred. No doubt it is this viewpoint which causes Amino's medieval "publics" (rooted in muen or kugai) to look so strange and different compared to the modern public sphere with its ideal of rationally debating citizens.
The word "vestiges" here is important. What interests Amino is not the sacred as such, but above all the sacred as a primitive force living on as a source of resistance to secular power in so-called civilized societies. There are certainly forms of the sacred that are comfortable with order and state power - we can recall Eliade's long discussions on states and cities modelled on a cosmic order in which sacrality increases with proximity to the center of power. Against this, there is another tradition that sees the sacred as located in margins and transgressions, in wandering and going beyond "civilized life". It goes without saying that what attracts Amino's attention is primarily the latter form of the sacred, but as his discussions of the Japanese emperor system show he is also aware - and, I would say, clearly troubled - by the former as well.
The interpretation of Amino as centrally preoccupied with the sacred as a force capable of destabilizing secular power throws light on the "emperor problem" in his writings, his ambiguity in regard to the "sacred" figure of the emperor whose prestige has repeatedly been used in Japanese history to destabilize secular regimes - from Go-Daigo to the "nativist" (kokugaku) scholars helping legitimize the overthrow of the Edo bakufu and to the rightist fanatics dreaming of a "Shôwa restoration" in the 30's.
In Japan, the figure of the emperor is in fact itself deeply ambiguous, lending itself to be seen both as a conservative patron of the establishment and as the object of the wet dreams of rightist revolutionaries, both as the personification of the kokutai (national body) transcending the seitai (apparatus of government) and as the figurehead of this seitai itself. This well-known ambiguity is at the heart of the controversy around Minobe's so-called "organ theory of the emperor": is the emperor an organ of state or does the emperor transcend the state? In relation to the two forms of the sacred, we can say that the sacrality of the emperor has been used throughout Japanese history both to sanctify the ruling order and to challenge it.
As I will show later, Amino rejects both these aspects of imperial power. But the problem is complex and I won't treat it here.