How the hell do you get to Otaru from Dunedin?
A yacht (would take a while)? An electric ship (would not have the range)?
By air (would take a while as you will need to go via at least two other cities, emits too much CO2).
As you can see there's no flights from Dunedin at New Chitose Airport (in fact they're almost exclusively from Asia).
For the moment the best way seems to be to Tokyo by air (via somewhere else about 15 hours or so) and then a couple of fast trains and one slower one to Otaru on Hokkaido (probably about another 10 hours). Or one train and a ferry (about 20 hours).
That's quite the trip. It looks nice enough once you get there though.
So I suggest we should seriously think of having one airport equidistant between Queenstown, Invercargill & Dunedin. So as we can have better connections. And fewer flights.
Of course you could also fly from Tokyo to Otaru (or at least nearby) but that seems rather vandalistic on environment when there are other options (which you could do overnight).