As I recall, this is a nice area called Himekawa, right before the main tunnel section. Note that the elevations are not that high; up to around 500 until you’re past the tunnels, and maybe another 200 from that point after you’ve passed the tunnels.

The real uphill starts just before an area called Otari, famous for the onsen area of the same name. There are several hot springs before and after (and in one case, between) the tunnels, at least one of which (I believe it was Himekawa Onsen) was recommended to me. I’m usually trying to reach Hakuba before dark, so I don’t have a lot of time to relax.