unfortunately, I will go on 27 July busy time.
bus will also fully booked because they can book online 1 month before, but I c't book until exchange voucher in japan.I am not 100% certain, but I think you can book the bus after you purchase the Takayama Hokuriku area tourist pass. This can be made by telephone. You should keep in mind the time difference and call when the reservation center is open. If you use some IP phone (like Skype), it won't be so expensive.
Nohi Bus Reservation Center
TEL (0577) 32-1688 9:00-18:00
Hokurikutetsudou Reservation Center
TEL(076)234-0123 9:00~18:00
can I upgrade to green car with pass to secure takayama wide view train?
if I not buy pass, where can I buy wide view train before arrive japan?No, there is no green car version of Takayama Hokuriku Area Tourist Pass.
Even if you are in the summer vacation season in Japan, it is rather unlikely
that all of Hida express is full for several days. There are 10 Hida express a day
and in general Friday night to Saturday morning is the busiest time. Other than
that time frame, you are likely to be able to reserve seat when do it a few days before.
You can check the availability through Cyberstation.
http://www.jr.cyberstation.ne.jpNote that Cyberstation works one month before since the JR reservation is
open one month before.
I am afraid JR Central (which operates Hida express) does not accept online
reservation from abroad, so even if you buy the normal ticket, you can't reserve
the seat for Hida express. At the worst case you can queue in the platform for
the unreserved seat of Hida express.