Mount Yudono is probably the most difficult mount to access, which only confirms its reputation of being the "most secret mountain of the Dewa Sanzan" (mostly because the main religion that is present on the mountain is Shingon Buddhism, an esoteric branch of Buddhism that is passed on through generations not by writings but by oral traditions).
In order to prevent accidents related to the heavy snow, the access road to the mountain is closed from November 4th to April 25th. Outside this period, you can go to Senninzawa's parking lot by car any day, any time.
To go by bus, possibilities are a little bit more restricted.
The bus circulates from June 1st to November 3rd, on very limited days. Here is the 2019 bus timetable:
Remember you still have the option to stay at the pilgrim lodge near the big red archgate: Yudonosan Sanrôjo.
To get more details, click here.
Or, if you are an advanced trekker, you can still challenge yourself to Rokujurigoe Kaido's Ancient Road.
Be careful, the trek is 7 hours long, and quite difficult to accomplish.
For more information about Rokujurigoe Kaido, click here.