I assume you mean the rindo leading over Hadano Toge to the lake. Actually a very scenic rindo - the views of Fuji-san (and also many of the Tanzawa mountains) are fantastic when the weather is good.
The rindo is paved, but is prone to landslides. I've done it a couple of times and it was never a clean ride. My most recent one involved very frequent crawls across big landslides. Some of them were so big and getting across them so cumbersome I doubt they have all been cleaned up by now and I cannot recommend trying it.