(by jrd_73 on 4 October 2018)

Although Ichikawa Raizo was deceased, Daiei Studios wanted to continue with the series, so Hiroki Matsukata played Kyoshiro Nemuri in this entry, subtitled Full Moon Swordsman on my copy. I came to the film after having read a few negative comments about this and the next entry (which I will watch soon).
Full Moon Swordsman had a lot working against it. First off, Ichikawa Raizo was well known for the role of Kyoshiro Nemuri after twelve entries. Secondly, Hiroki Matsukata, a good actor, had a face that seemed to belong to a more modern period (which was why he was good in yakuza films). Thirdly, the make up department made Matsukata look like some sort of deranged owl, not a pleasing image. Finally, Full Moon Swordsman came after four of the best entries in the series.
As a movie, Full Moon Swordsman was just okay. It was a decent samurai adventure. The plot had the shogun's successor being replaced by his twin brother, a pawn of the inspector general. Nemuri got involved after rescuing a woman seeking revenge for her murdered brother (he had guessed that the successor was an impostor). Other plot complications included a female government spy and struggling children whose father was an imprisoned farmer.
The action scenes were decent, if lacking a standout sequence. The best was Nemuri's nighttime showdown with a group of Iga ninjas early on in the film. As for the story, it felt by the numbers. The plot was workable, but did not generate much emotion for this viewer. Again, had this story been early in the series, it might have seemed more meaningful, but coming after the last four entries. . . .
Full Moon Swordsman was not as bad as some people have said (although I should mention that the other reviewer here liked the film a little more than I did). Rather, the film was merely average, on par with, say, The Chinese Jade, the first film in the series.