Getting Around
Furano
The sights around Furano are not easily reachable via public transportation.1 One can get around on rental bicycles. If arriving via air, a bicycle can be rented over multiple days from Fuji Shoukai in Asahikawa.2 If you arrive by train in Furano, it's possible to rent an electric bike from the Furano Nature Club, but it seems one must rent on a day-by-day basis.3 However, it may be best to just bring one's own bike and pay the fees to transport it via the train.4
If you do not want to bike, then the sightseeing buses are an option. However, the buses mainly only run during summer months, and are not a serious exploration option.
Yokohama
Yokohama has a very complete transit system. While central Yokohama can easily be explored on foot, there are two buses that loop around central Yokohama: the Bayside Blue Bus with an endpoint at Yokohama Station, and the Akaikutsu Bus with an endpoint at Sakuragicho Station.5
If you fancy sightseeing, then you have the option of a voyage along Yokohama's bay area via the Sea Bass (wordplay on "Sea Bus"6). It has a stop at each peninsula, as well as one near Yokohama Station.7
Fukuoka
Fukuoka has a subway that connects most major locations, including Hakata Station, the city's main station, and Fukuoka Airport.8 A cheaper option will be the Nishitetsu bus lines, with a route map9 so comprehensive that many computers will struggle to render it.