Updating my post for anyone interested in the future.
I completed the Daisetsuzan traverse in Hokkaido solo in 7 days with 2 bad-weather hut days in late October. There was snow/ice but conditions were generally quite good. Crampons were essential (ice on the steeper sections of the peaks) and snow shoes were helpful (very deep snow in some sections, particularly in the lower flatter areas). Route-finding was generally fine even with the track covered in snow, but I had good visibility apart from the 2 enforced rest days and the maps I had were very good and accurate.
In good visibility I found the going fairly straightforward. The most difficult walking is between Mt Tomuraushi and Tokachidake where there is some thick vegetation made more difficult with snow on top, and some steep narrow ridgelines where mountaineering/climbing experience was helpful (steep exposed ice with bad fall potential).
Because of the season and conditions I had the entire park to myself – I saw nobody between the Asahidake ropeway (day 1) and the Tokachidake onsen (day 7). I did come across fresh bear tracks in the snow but luckily I did not meet any bears (but I made a lot of noise singing to myself as I walked).
I certainly would not recommend the walk to someone without winter experience, but for an experienced winter walker or climber it is a fantastic time to enjoy the region.
