I went on a day-long hike by myself to Mt. Nabewari and Tonodake in Tanzawa, Kanagawa. The route covered 21.27 kilometers, with a total elevation gain of 1,395 meters, and it took me roughly 9 hours to complete (break and sketching time included). 
I kicked off my hike from Okura bus station and then headed west towards Mt. Nabewari (just follow the signs). If you go north there is a route that goes to Tonodake directly. To access the Okura bus station, you need to take a bus from Shibusawa Station (Odakyu Line), which takes around 15 minutes. Just be aware that on weekends or holidays, the bus can get pretty crowded with fellow hikers! 
Also please take precautions as you are hiking up Mt. Nabewari for there are mountain leeches in the area, especially during warmer seasons. Bring a bag of salt or a leech spray with you just in case. I never got bitten, but I had a friend who did, unfortunately. 
The level of the hike I would say around high intermediate although it is not so bad for novice hikers as well, unless you are really fit. 
Gears:
Backpack - Yamatomichi Mini Zipper
Boots - Altra Running
Camera - Sony Alpha 6600
Lens - Sony 135 mm

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