JR Tokyo Wide Pass to KAWAGUCHIKO

Hi

I'm quite confused about JR Tokyo Wide Pass travel to Kawaguchiko. I know this pass covers Fujikyu Railway. But is it also eligible for use on FUJISAN VIEW EXPRESS? If I sit on FUJISAN VIEW EXPRESS without reserving a seat, is it permitted?

Yes. It is pretty clear on the JR East web site and also the Fujikyu website that the Tokyo Wide pass works on Fujikyu railways for the local, rapid, limited express trains (you will need a reserved seat ticket) and the Fuji Tozan Densha (seating ticket required).
http://e.fujikyu-railway.jp/