Sapporo kani-honke is faimous restaurant in sapporo.You can eat several crabs &crab couse there.
I have met few people from Hokkaido, but for people in Hokkaido, crabs are not a thing to eat outside usually. They buy raw crab (sometimes a live crab!) at fish market or supermarket, and boil it at home.
When I went to Kushiro, I found a UFO cather of live crab!! Surprising, isn't it? I caught two crabs :D