Depending on traffic conditions, it takes usually 65 minutes to reach Tsukuba Center. The timetable can be found here . The bus system is Tsukuba is relatively easy to use. This ticket has a number indicating your starting point. Beware that 5,000 and 10,000 banknotes cannot be changed in buses, so carry enough coins or a 1,000 yen banknote.
Buses are quite frequent.
This is equivalent to saying that you should avoid all campus buses. Disembark at Tsukuba Center bus terminal. The fare is 260 yen. It takes about 100 minutes to reach Narita Airport from Tsukuba Center. You have to buy a ticket at the Kantetsu Kanko office on the ground floor of the bus terminal building.