Sagamihara is a big city on the western edge of the Tokyo sprawl, but it stretches surprisingly far into the mountains. Its western part takes in the Tanzawa foothills, Lake Sagami and Lake Tsukui, two reservoirs on the Sagami river surrounded by forested hills, and the change from suburb to mountain happens quickly.
The city has a space connection: the Sagamihara campus of JAXA, the Japanese space agency, managed the Hayabusa missions that returned samples from asteroids. There is a small exhibition hall open to visitors, and the city is proud of its role in space exploration.
For riders, the high ground west of Sagamihara is the start of some of the best roads near Tokyo. Route 413, the Dōshi road, runs from Sagamihara through the mountains to Lake Yamanaka, near Mount Fuji, a long, winding route through forests and valleys, with countless bends and a few steep climbs. It is hugely popular with motorcyclists, and on weekends you will see many of them, as well as at the roadside rest areas along the way.
Traffic can be heavy, especially on weekends and in the autumn foliage season, and the roads can be narrow, with blind corners. Watch for cyclists, oncoming traffic cutting corners, and wildlife, including deer and monkeys. Fuel is available in Sagamihara and at a few points along the route, but stations are sparse in the mountains, so fill up before you go.