>>2023350It actually doesn't travel from Honshu to Hokkaido like the sleepers, JR Hokkaido just rents the trainset from Izukyu plus a MaNi 50 car from JR East (to power the trainset) and uses two DE15 locomoatives to tow them. The 4 Day / 3 Night itinerary basically travels around the eastern portion of Hokkaido before returning to Sapporo.
https://www.the-royalexpress.jp/plan/3327/