What is one theme in detail?

Yuranosuke's story is one of loyalty. He is the idealized samurai archetype, his sense of duty outlasting even the life of his lord. In essence, this means that Yuranosuke's loyalty is in no way compelled by external forces. There are no laws governing his behavior, no promised rewards or threatened punishments. Yuranosuke acts purely of his own accord, driven by his own sense of justice and love for his lord. In this respect, Yuranosuke is never truly a ronin, as he forever serves a master.

Not all of Lord Hangan's samurai prove so loyal as Yuranosuke. Kudayu finds fault in his lord's behavior, even suggesting that Hangan was foolish to make an enemy of Moronao. Kudayu's calculated pragmatism is soulless, leaving no room for the moral reasoning necessary to justify Lord Hangan's behavior. This explains why Kudayu later enters the employ of Moronao, the sworn enemy of his lord. To Kudayu, it's not a question of loyalty, but a question of making the right friends to achieve the most desirable results.

Chushingura offers several examples of imperfect loyalty producing undesirable results. Honzo interferes with his lord's vendetta against Moronao, violating the spirit, if not the letter, of his promised non-interference. As a result, Moronao is not killed by Wakasanosuke and thus lives to offend Lord Hangan. Similarly, Kampei allows himself to be distracted by the lovely Okaru, ensuring that no one is beside Lord Hangan to dissuade him from attacking Moronao. The story's implication is obvious: Loyalty is necessary for a just society.