Fom Shinjuku to Subashiri 5th Station bus?

Please confirm reg. schedule and how do I make a reservation for this bus? 8/31

There is no such bus.

There are buses from Shinjuku to Fuji Subaru 5th Station, which require seat reservations.
And local buses from Gotemba Station to Subashiri 5th Station, which don't allow for seat reervations.

Reservations for the above bus can be made by phone (03-5376-2222, possibly no English), at the bus terminal and at the following Japanese website:
https://www.fujikyu-travel.co.jp/dp/dpBusTop.html

And I just discovered the following English reservation website:
https://www.highwaybus.com/gp/inbound/inbPlanList?lineId=110