In the introduction to this novel, it seems as if Endo had a Western audience in mind for this novel (though he wrote in Japanese) because he writes an introduction introduces some historical context for the reader who wouldn’t be familiar with Japanese history. That context is in the years of first contact with Europe by way of Catholics missionaries (Dominicans in this novel if I recall correctly), and prior to the full on cultural invasion of those same missionaries in that next two centuries.
So the novel involves a low-ranking samurai being released from prison in order to become an emissary to Spain, by way of Mexico, with a Catholic priest returning to solicit further missionary projects in Japan. The samurai had decidedly mixed feelings about being released from prison only to be sent away from his family again on this mission. This is in addition to the fact that he’s not Catholic, doesn’t wish to be Catholic, and doesn’t really understand the point of the mission. The mission ultimately is about creating trade routes with Europe, and seems to come at the cost of allowing for potential conversion/Christinization of Japan.
The novel is mostly told through the narration of the priest, which makes it incredibly fascinating to have a Japanese writer take on the voice of a Spanish priest looking at Japan as a well-informed outsider. It’s a fascinating premise and often the novel is very good. It’s plain and straightforward as well, and so the reading is dry, philosophical, and measured throughout. There’s a lot of tragedy and death that is read through this outsider’s lens, which can be both heartbreaking and infuriating as well, and the priest, the samurai, and a few of ther envoy really stand out as stellar characters.