One of the best MTB trails in Japan. It is located in the foot in the Mt. Amagi, Izu paninsula, 3 hours drive south from Tokyo. You ride on the somma in the dormant volcano, which goes down to the ocean at the end.
The route is a combination of paved road 30%, fire road 35%, and single track 35%. You climb 10 miles with 3000 feet elevation gain. After gotting into the single track in the forest, you forget you climb allthe way up there. It is fun!
For safety:You ride on the hiking trail. Like other trails in Japan, we share the trail with hikers. Be aware of hikers. When you see them you get off your bike and say "Konnichiwa!"
More detail:There is trail guide tour which takes you to the trail head and proveds guide service. AlohaBiketrip http://www.alohabike.com