On the north-western part of the Izu peninsula there are several towns were fishing is still the key economic driver. Following the route 17 from Numazu or Izunokuni along the coast gives a scenic views of these towns with sight on Mount Fuji in case the weather is clear. After approximately 10 kilometer there is entry to the route 127 which were the good driving road starts.
Coming from the north, this part of the route 127 is climbing up the mountain with a lot of sharp corners and few hairpins. The road will end up at a T-section where the choice is route 18 down the mountain (right) or route 18 up the mountain (left). Go further up the mountain to find even more challenging corners. Soon the road will merge into the route 127 again.
At the top there is an intersection (including a parking) with route 18 leading down the mountain to the hot spring town called Shuzenji. Go right on the intersection and you can continue to follow the route 127. See the Nishi-Izu Skyline (pt. 2) to get to know more about this route.
At the time of writing these roads are toll free.
Google Maps location link:
Entrance to route 127
JDM4all Youtube video: