From Narita to Imizu in Toyama

Hi, I plan to travel to Toyama on October. I tried to book a bus through willer express to get to Toyama from Narita but the attempt was not successful. Perhaps, the website had some technical problems. I'll visit again on another day. I hope someone can give me detailed instructions how to get on a bus from Narita to Toyama. For example, what to ride and where to ride a transportation from Narita airport to go to the bus station headed for Toyama. I'm on a tight budget so I want to travel mainly by bus. What time do buses usually leave so I can book a flight that can meet the bus schedules and arrive in Toyama on the same day? Your responses will be greatly appreciated.

The only direct bus route I found on Willer Bus was from Narita Airport No. 3 Terminal (21:20 departure) to Toyama Station (6:50 arrival), for a random date in October.

The bus stop at Narita Airport is bus stop number 7 at Terminal 3. Note that Terminal 3 is a bit away from 1 & 2 terminals.

Thank you AK. I see it's going to be an overnight ride. I'm sorry I have to ask another question, do I have to buy a bus ticket in advance or can I just buy on the day that I will ride the bus?