Onuma Koen(Onuma park) station is located on JR Hakodate main line.
If you get off Hokkaido shinkansen at Shin-Hakodate Hokuto, you can take a local train bound for Mori or Oshamanbe, or limited express Super Hokuto or Hokuto bound for Sapporo.
It is 10 minutes from Shin-Hakodate Hokuto and 25 minutes to Hakodate by limited express.
However please be aware that several limited express trains do not call at Onuma Koen, especially in the early morning and in the evening,
This station is the gateway to Onuma national park which is very ideal place for trekking and cycling. You can rent a bike outside the station easily.
For JR pass holders, the limited express Super Hokuto and Hokuto are known as very crowded due to connecting Sapporo, the capital of Hokkaido prefecture and Hakodate the third largest city. Recommend to do the seat reservation in advance. The limited express has 7 cars but just 2 non-reserved cars.