Okay, place location time.
The "Northern Province" that Usagi's village is in is likely Mutsu. Apparently the tournament where Usagi first met Katsuichi and lord Mifune took place in Sendai, which is the closest large city.
Geishu lands are somewhere on western Honshu. A tremor at Dan-no-Ura was felt strongly at their castle, which may or may not be Himeji based on its name.
As for Katsuichi's hut, well, it's kinda fuzzy, as we don't have anything to go by. Far enough from Sendai that the travel took a couple of days.
I can't remember if we've ever been given the name of the city where Ishida lives, but I faintly recall that it's Nagoya.