Your research will be interesting. The motivation behind the transplanted style should tell you a good deal about the builders and owners. Were they western? Was there a expatriate society? Was there a design convention that tired of the prevailing architecture and wanted to simply try other forms? Did Japanese builders use western building techniques or their own? Does Tiny Reactors want to bother with so many unimportant questions?
Yes, Tiny Reactors might bother, though when Tiny Reactors gets around to bothering is quite another matter. Thought you might have some questions. I do know that Saihei Hirose, who was the 35th General Manager of the Besshi Copper Mine (this town was built on copper) just after the Meiji restoration in 1897 not only invited French engineers over to give technical advice, but he constructed his own house which featured many Western adaptations such as lightning rod, glass windowpanes, and toilet. Emmy & I have been through that house (a museum now) though I didn't take pictures at the time. I'll go back and get some. There could be some connection to the houses on the blog. Not sure.