The real life Mesmer

When the detective was looking through the books there was a book on France and one with a french title. I can see how it would be almost commonplace to assume that he was in Japan, but they never connected him with Japan in anyway except for the research that was done on him there.

The Edo period (Japanese: 江戸時代, Edo-jidai), also called Tokugawa period, ended sometime around the 1860s, at which time Japon ceased to be isolate from the rest world, therefore, Franz Anton Mesmer, a homebody, and, having died in 1815, could not have visited the Land of the Rising Sun, unless having voyaged there via ocean-going non-trade type frigate. In the time of this writing there are only three books written in the Japanese language concerning Mesmer. Kiyoshi Kurosawa claims to have read all three . . . . . . .

I'm not sure if the movie alluded to the fact that Mesmer had been in Japan. What I remember is that Sakuma says that earlier in Japan hypnosis was seen as occultism, and therefore repressed by the state.

But there's a shot in the movie of a book titled "Heresies", and in it there's a chapter called "Mesmerians" (or something like that). In the following page there's someone's picture -- but the face in the picture is blank. By the end of the movie, when Takabe is just about to kill Mamiya, they are in a house inside which we see what appears to be that same picture in the book, only this time the face is more visible, and it looks like a japanese man.

I'd say the idea of a follower of Mesmer is the most plausible one. Maybe the house they're in was the hospital or clinic this follower worked at (the place reminds me of an old, abandoned clinic).