Chichibu-Tama-Kai is the least visited of the national parks within easy striking distance of Tokyo. With eight peaks over 2000m scattered over 1250 km2, there are plenty of hiking opportunities and ancient shrines to visit.
The most popular access route is on the Seibu Chichibu Line (西武秩父線) from Ikebukuro in Tokyo to the terminus Chichibu station (75 minutes, ¥1370 via limited express).
For access to the Oku-Tama region, take the JR Chuo line to terminus Ome (75 minutes), transferring at Tachikawa if necessary. From here, transfer to the Ome line; a trip to (eg.) Mitake station from here takes 20 minutes and costs ¥890.
It is possible to hike Mitsumine and Mitake either separately as day trips, or as a full day's hike along the trail connecting the two.
Mount Mitsumine (三峰山 Mitsumine-san). Home to the 2000-year-old Mitsumine Shrine (三峯神社 Mitsumine-jinja, ) on the summit of this fairly tame 1100m mountain. From the Chichibu Railway Mitsumine-guchi (¥ 950/1650 one-way/return, every 30 min from 9 AM to 4:30 PM) walk directly across the street to the bus station, there you can take a direct bus to the top (¥ 670 one-way) or via a direct bus from Seibu Chichibu station (¥900, 5 daily). Still, you may find it more rewarding to hike up (or down), there are some nice views and waterfalls along the way and you can pop in at the shrine ryokan Kounhaku's onsen baths for a refreshing dip at the top (¥500). To get to the hiking trail take the bus from either Chichibu station and get off at Oowa (大輪), you'll see a large shrine gate, price depends on either station, from Mitsumine-guchi 310 yen one-way, from Seibu Chichibu about 500 yen one-way.
Mount Mitake (御岳山 Mitake-san). Follows a very similar pattern, with the Musashi-Mitake Shrine (武蔵御嶽神社) up top. Take a bus from Mitake station to the Mitake cablecar (10 min, ¥270), then the cable car up to the shrine (¥1090 return).
Kōunkaku (興雲閣). Tel. 0494-55-0241, . A ryokan operated by Mitsumine Shrine, located in the large modern concrete building smack dab in the middle of the grounds. Basic onsen baths included. Rates from ¥10,000 with two meals.
Be aware that landslides occur in this region. Check the weather report for heavy rains. When walking in the mountains make sure someone knows where you are starting from, where you are going and what trail you intend to use. There are paper slips at most trails that should be filled out with name, address, route and contact information for nearest relative. An exit slip is filled in at the end of the trail.