Aomori to Lake Towada via Sukayu Onsen

In mid-April I am planning to fly to Aomori and take a bus to Lake Towada as I hear that this bus route is very scenic. The Sukayu Onsen is on the way and I wish to stop for a hour or so too. Can I walk from the Sukayu Onsen bus stop to the onsen (sennin buro)?
According to
http://www.jrbustohoku.co.jp/english.html
there are only two buses from Aomori to Towada-ko. Is this route so poorly serviced or is the time table for the off-season or are these just the buses that take the JR Rail pass? The Japanese section
http://www.jrbustohoku.co.jp/sightseeing_img/aomori-towadako...
shows more buses and they are faster as well but not knowing Japanese I cannot judge which is correct!
Many suggest to walk the final journey from Ishigedo to Towada-ko beside the Oirase-gawa. The second bus from Sukayu Onsen reaches Ishigedo only at 4:45pm. Will this be too late in the day to make this walk? What time does the sun set?
Thanks in advance, Andrew.

Can I walk from the Sukayu Onsen bus stop to the onsen (sennin buro)?

Of course. The onsen is just beside the bus stop.

Is this route so poorly serviced or is the time table for the off-season or are these just the buses that take the JR Rail pass?

A note says "It is time from November 1 to March 31." So obviously, this timetable in English is for the off-season and has not yet been updated to the on-season version while the Japanese one has already been done. It's a shame.... I would rush them into doing it with the English version as well if this site had an email address.

According to the Japanese version, the second bus from Sukayu Onsen (at 10:12) reaches Ishigedo at 11:09.
You should note that a walk from Ishigedo to Towadako will take you about 3.5 hours or more. Though I don't know the accurate sunset time in Aomori in mid-April but I suggest you to reach Towadako before 5:00 pm.