Bus
You can catch a bus to Syounkyo from Asahikawa. Syounkyo is a hot spring resort just below the Kurodake village. Buses leave 8 times a day.
Hire car
Pick up a car from Asahikawa or Sapporo to get up to Kurodake. The car may be useful for the more adventurous as there are plenty of mountains to explore along the road heading out of Kurodake to the North.