This movie is a clear homage to Seven Samurai: it concerns the recruitment of 13 samurai for a mission, in which they booby-trap a village to defeat a much larger force. Featured among the group are a miraculously strong simpleton, a young samurai eager to prove himself (arguably two), and the veteran Shinzaemon.
13 Assassins adds a vile antagonist – the detestable Naritsugu, with sadistic arrogance straight from a Yamada Futarou novel – and his bodyguard Hanbei, whose idea of bushidou revolves around loyalty and conflicts with Shinzaemon trying to serve the people.
There is a touch of typical Japanese overacting, gratuitously nasty scenes, goofy slapstick humour, and pointless sacrifice, but the core character conflicts are interesting, the battle scenes are good, and there are some nice touches – such as the incomplete white makeup of many of the women.
I recommend this movie for fans of samurai films.