The classic traverse is a two-day hike that stretches for 25km from Iwaobetsu Onsen (岩尾別温泉) to Kamuiwakka-yu-no-taki (カムイワッカ湯の滝). You'll need to be properly equipped to tackle this route. Starting from the trailhead at Iwaobetsu Onsen, you'll climb Rausu-dake (羅臼岳; 1660m), traverse along the top to Iō-zan (硫黄山; 1563m), then descend to Kamuiwakka-yu-no-taki, a 'waterfall onsen'.
There are four camping areas along the top that have steel food bins (think bears!). Don't underestimate the difficulty of the terrain. The last bit of this track has been reopened. Drop in at the Shiretoko Nature Centre for the latest on conditions and advise staff there of your intentions. The trail is officially open from mid-June through the September holiday period, though snow and extreme conditions make these shoulders inadvisable for all but the most extreme (and prepared!) hikers.