Currently the bullet train (shinkansen) line is running from Tokyo to Shin-Hakadate in Hokkaido and will be extended to Sapporo, stopping at Kutchan Station.
The extended railway line is expected to be completed in 2030, although there are rumours circulating that it might be completed as early as 2024. It is expected that the Tokyo to Sapporo route will take just 5 hours and 1 minute (faster from Tokyo to Kutchan Station) allowing for a feasible alternative to air travel.
Currently, the Niseko Tunnel for the new shinkansen is underway and according to Niseko Town’s update for the Hokkaido Shinkansen it is 14% complete and on track to be finished on time.
Using current trains and train lines, the Tokyo to Kutchan journey takes approximately 6.5 hours and will cost about 26,000yen for a regular shinkasen seat ticket + local trains.
If you are wanting a more spacious and luxurious journey on the Shinkansen you can buy a GranClass ticket which includes a folding table, adjustable lighting and reclining chair with controls and buttons for calling attendants.