Can I use JapanRail Pass for the JR Kanto Bus from Tokyo station to Kawaguchiko ?

hxn

I plan to go to Kawaguchiko from Tokyo. There is a Kanto Express bus from Tokyo Station to Kawaguchiko. Can I use JapanRail pass on this bus ?

Tenjin

In short, no.
Your options are here:
https://www.japan-guide.com/e/e6905.html