High up in the mountains, this cluster of onsen ryokans and inns have rotenburo, konyoku (mixed gender) baths, among others, in an idyllic mountain valley setting overlooking Lake Tazawa (田沢湖).
Top to recommend are Tsurunoyu (鶴の湯温泉), with stunning, milky-white water and a large rotenburo, and Kuroyu(黒湯温泉), which for bus-goers requires a short 10-min walk along a riverbank. Kuroyu overlooks the river valley and has a number of different baths, both indoor and outdoor. Kuroyu's konyoku rotenburo has a stunning view, made even nicer in autumn with the changing leaves. Ganiba Onsen (蟹場温泉), the last onsen at the end of the road, has a beautiful konyoku rotenburo that should not be missed, along with some excellent uchiburo. Magoroku Onsen (孫六温泉), as expensive as the other places, is either currently under construction or else needs a reassessment of the details. Tepid rotenburo, unatmospheric plastic pipes crisscrossing the area, and baths with plastic weights in them make for a less than idyllic soak, and compared to the nearby alternatives, Magoroku falls flat.
If price is not a factor, choose to stay overnight at one of the establishments, as the bus is infrequent enough and the higaeri hours are not exactly in sync. You'll have much more time for relaxing yumeguri (onsen hopping) if you stay overnight here. However, there are a number of very reasonable options for lodging closer to Lake Towada, and the youth hostel's Japanese-style meals are excellent, using lots of local and in-season ingredients. Either way, Nyuutou Onsen is sure to be a highlight of an onsen vacation.