Mount Gozen (御前山; 1407m) and Mount Tsukiyomi (月夜見山; 1147m) are mountains bordering Lake Okutama (奥多摩湖), in Okutama in western Tokyo. With Mount Odake and Mount Mito, Mount Gozen is one of the so-called Three Mountains of Okutama (奥多摩三山).
I basically followed the path outlined in this Japan Times article. Another good resource is this map of trails around Lake Okutama.
I started the hike at the Ogouchi Dam in the morning and set out for the summit of Mount Gozen. On the way, I passed through the summit of Mount Sasuzawa (サス沢山), which offered a good view of the lake. After reaching Mount Gozen, I walked through Ogochi Pass on the way to the summit of Mount Tsukiyomi. From there I continued west, towards Sayaguchi Pass (鞘口峠) but the trail was shared with the road and I didn’t like it much so I doubled back and instead went down to the so-called Parking Area #1 of Mount Tsukiyomi (月夜見第1駐車場). It was a good decision since the view of the lake and the surrounding mountains were great. Finally, I took an unmaintained trail that followed the mountain ridge all the way down to Lake Okutama and the Ikoi trail (奥多摩湖いこいの路). I then followed the trail for a bit and walked across the lake using the floating Drum Bridge (Mugiyama-no-Ukihashi; 麦山の浮橋) to reach the bus stop.
Above, on the empty Ogouchi Dam.
Above, view from the summit of Mount Sasuzawa.
Above, view of Mount Kurato and Mount Kayanoki.
Above, path from the summit of Mount Sogaku. Mount Gozen was about 15min from there.
Above, Mount Fuji viewed from a rest area just before the summit of Mount Gozen.
Above, summit of Mount Gozen.
Above, leaving Mount Sogaku for Ogouchi Pass.
Above, Parking Area #2 of Mount Tsukiyomi (月夜見第2駐車場).
Above, I had to walk a short section next to the road to reach the trail to the summit of Mount Tsukiyomi.
Above, summit of Mount Tsukiyomi.
Above, mountains to the west. The white structure at the summit of Mount Otera is an abandoned Peace Pagoda.
Above, Road 206.
Above, trail to the Parking Area #1 of Mount Tsukiyomi.
Above, view from the Parking Area #1.
Above, view of the summit of Mount Gozen.
Above, the western area of Lake Okutama. The floating bridge can be seen.
Above, on the way down to the lake. The trail was not marked very well. I got lost at some stage and ended up at an almost vertical section just before reaching the lake.
Above, the Ikoi Trail where I emerged from the forest.
Above, the floating bridge, viewed from the north bank of the lake.