This is a summary of Kōji Kawamoto’s theory of Japanese poetic metre. I am writing it from memory (quite distant memory, in fact), so it probably contain errors or half-remembered things. As such, it’s not really a reliable source for your thesis. But you’ve seen just how hard is The Poetics of Japanese Verse to get a hold of these days; it’s not on the usual online sources, it was nowhere in the libraries of Dublin or Bochum, & on bookstores it has reached the triple digits, in the manner of academic books under late-stage capitalism. By now you can finally access a copy, like some fabled treasure, at the same place I originally found it: in the charming little library of the Japan Foundation, São Paulo chapter. But I fear that, at this point, it might be too late. Kawamoto is dense reading; I had to make two or three separate attempts, each one exhaustingly intensive, until I felt like I had digested the gist of it. And of course at this point you can’t afford to muck around with the tarpits of one-more-source. That’s why I’m writing this summary, however lacking my memory is. You can’t of course cite something like this; but maybe you can use it to guide a brief look through Kawamoto’s book, pick out some choice quotations, and use this theory in an academically responsible way.
(I will drag a bit to get to the main point—well, you know me. Skim near the bottom for the meat of the thing, i.e. how to find rhythms in Japanese poetry.)