Okama Crater from Zao Onsen

Hi,

Is there a bus between Zao Onsen and Okama Crater? If yes, can you help with English timetable please?

Thank you.

Access is explained here:
https://www.japan-guide.com/e/e7929.html

Usually there is one round trip operated per day between Zao Onsen and the Kattadake peak from late April; however, that part of the route is suspiciously absent from the 2018 timetable:
http://www.yamakobus.co.jp/rosenbus/jikoku/frame/zao-onsen.html

I am not sure whether they will announce that part of the timetable later (should happen within the next three weeks) or whether they may not operate the bus this year.