You can take an express train from JR Shinjuku Station to Matsumoto Station.
I advise you to bring your own Brompton.
At Matsumoto Station, change to Matsumoto Railway to go to Shin-Shimashima Station.
At Shin-Shimashima, please get bus to Kamikōchi.
It takes about an hour and half to Kamikōchi Bus Terminal.
Nature of Kamikōchi is perfectly preserved.
A group of wild monkeys are also well preserved. Hi!
"JAPAN ALPS KAMIKOCHI Official Website"