This is the third entry in the published Sleepy Eyes of Death series although there are a couple of Sleepy Eyes made in the 50's before The Chinese Jade. A typical story in the series is a collage of sub plots that involve Nemuri in one way or the other that get resolved progressively until we arrive at the climax where he squares off with the villain and his henchmen. Full Moon Cut involves a concubine of the Shogun who schemes to have her son become the sole heir to the throne, a poor commoner who wants revenge from said concubine's son for killing his father to test his swords and a woman Nemuri becomes romantically involved with until her husband returns from exile and is paid to kill him.
The assortment of motley characters that often populate this kind of pulpy b-movie chambara aid or oppose Nemuri depending on which side they find themselves in but it's not completely a case of good-evil here. An example is a poor, honest samurai that is challenges Nemuri to a duel. Nemuri also rapes his antagonist's wife and as Ichikawa isn't the rough hewn and big type like Mifune or Katsu, we get the impression that something other than brute force is at play, maybe some sort of evil, sly charm.
Even as he is confronted by the poor samurai that needs to kill him in order to pay back a debt of honour, a noble act in itself which partly confirms there's still hope for the samurai class, Nemuri doesn't stop his scathing attacks at the samurai principles he despises. This is not a "I will speak daggers... but use none" case though: the man is a hardass when it comes to using a sword and the movie ups the ante in terms of violence from the previous Sword of Adventure. There's a chopped head and limbs and a nice final fight on a burning bridge where Nemuri is framed by flames before he delivers the fatal blow, like some kind of sword devil (to use a Kenji Misumi title Ichikawa starred in one year later).