Hey, I was wishing to inquire the plausability of Japan being a similar case to the British Raj considering pre 1920's Britain and Japan had very good relations ( the Japanese navy being trained by British officers and such ) so is it possible maybe after 1850 Japan being colonised, or partially colonised with Protectorates led by local shoguns... or even a divided Japan with different islands being colonised by different nations? Just thought a British empire with India as its jewel and Japan as its sword was a cool idea
I'd say that most of Honshu is unlikely to fall under foreign occupation, it's densely populated and very, very integrated. Also, keep in mind that by 1850, Japan had been ruled by the Tokugawa bakufu for over two centuries, and there was probably little incentive to rock that boat.
Shimazu on the other hand is a totally different matter: it was considered a backwards place by the Japanese, and was always given a lot more free reign than the rest of Japan, essentially being the door to the outside world (even during isolationism). From there, it's not entirely unlikely that a foreign power funds and supports one Daimyo over another (probably Satsuma, since it was the most prominent) and has him bring the entire island under his control, and then having him be the "puppet" so to speak.
Still, I can't see that lasting very long once the central government decides to reestablish control, unless this occurs far back enough that it is essentially a different country (maybe the Dutch, Portuguese or Spanish decide to take a far more active role in Satsuma than they did OTL in the XVIth century).