From Utoro Onsen to Memanbetsu Airport

I will be staying at Utoro Onsen for my visit to Shiretoko National Park in September. I intend to fly from Memanbetsu Airport to Tokyo at the end of my visit. Where do I purchase bus ticket to travel from Utoro Onsen to Memanbetsu Airport? Is it at the Utoro bus terminal? Do I need to book in advance?

reservations not necessary.
http://www.sharibus.co.jp/pdf/ShiretokoAirPortLiner27.06.13.pdf

Thank you for the link to the timetable. It is stated that no reservation is required but it does not say where to buy the ticket. Is it at the Utoro bus terminal?

As the bus stops to pick up passengers at various hotels and other places along the way I would presume that you pay on board (no ticket required).

Thank you.

My suggestion is, try to contact your hotel to ask if they would be able to book the bus ticket for you for Utoro onsen to Airport or if they have special chartered bus on their own to Airport.

When I was there this February, I saw the hotel I was staying in has their own chartered bus, not sure going where though.

Thank you very much. I will do that.