Marumi prides itself on its gut-busting seafood banquets, making this a good choice if you've worked up a calorie deficit in the mountains. The Japanese-style rooms themselves are simple with shared facilities (you can upgrade for an ocean view and an en-suite bath), but there's an outdoor onsen facing the waters.
The modern, concrete ryokan is 8km southwest of Rausu on Rte 335. Marumi also does cruises to see whales and dolphins and, in winter, to see the drift ice; enquire about packages when you book.