It sounds like there were smaller fireplaces that shared a chimney route? Or is that just the stone shared a pathway, not the actual gap that let the smoke escape?
What about in multi storied buildings in areas like Japan where it was normal for hearths to be in the middle of the room and set into the floor?
Hi! I'm a historian for a park system in the States which oversees several 19th century structures. One house, a 4 story stone Federal style home has 7 fireplaces. The north/south ends of the house, per the Federal/Georgian manual of style, each have a main fireplace system. All the fireplaces feed into it. On the bottom level in the kitchen, the fireplace feeds directly into the chimney. On the upper levels theres a flue/channel that feeds backwards into the main chimney stack.
This is the case for most of the 19th century homes. You can actually look up architecture manuals of style on Archive.org! They're fascinating to read!
Sorry I cant provide more context for Japan.