Hello. Yes there are buses that travel around the lake and there is even a tour boat or two on the lake itself. The bus from the Tazakawa JR Station to the Lake leaves about every 20-30 minutes and once you get to the lake the bus that circles the lake comes around every 40 minutes I believe *you can see the time table when you arrive). However, the buses in this area tend to stop running around 6pm, I suggest you arrive early for everything. Also, pay attention to the how the bus picks you up when you're leaving, everyone makes the mistake of standing where the drop-off area is.... that's not where they pick you up to bring you back to the station. I also think you can't find a bus schedule because it changes seasonally or it's only in Japanese. Have fun!

We took a bus down to visit the lake - about 25-30 minutes from Mizuwa-sanso (bus stop was across the street a bit below, 2-3 minutes on foot). We spent about an hour on a bicycle (Y400 per hour per bicycle for the first hour, then less for next hour). One hour might not be enough to bicycle around the whole lake though. Then we took the boat (Y1200 per person, find a coupon for Y100 off). You can take a bus tour instead which goes around the lake and stops at I think 2 or 3 spots for a few minutes for pictures: statue of Lady Tawazako and a shrine (looks about the same as most shrines in Japan). There are shops and restaurants in the same place as bicycle rental, boat, and bus stops. The buses are quite infrequent (about 1 per hour and sometimes longer between), so a day trip on a bus should be planned carefully. We were very underwhelmed... - our favorite was bicycling around the lake a bit.

Hello, I did not stay at the Nyuto Onsen. But I understand the buses run from Tazawako JR station every hour or so around the Lake and up to the Nyuto area. I am away from home at the moment so can't get to my trip records. I am certain I did download a timetable from somewhere.