I had visited Tsukuba Science City, Japan, for a conference and this post is mostly about what i did and what i missed.
The bus website
is the right place to look at for updated info. Most people were suggesting as if we need to book in advance. I reached airport by around 9 AM, and was comfortably able to get a ticket. (2540 yen).
This is a very good deal, and also the most comfortable option. If you are stupid like me, and thought of appreciating the scenic beauty on the way to Tsukuba, nothing can be done about it. Tsukuba is much greener anyways, and you can spot a lot of paddy fields in other parts of japan as well. The biggest plus point for this bus is that it won't go fast. Unlike our Indian buses, you can tilt back the seat and sleep peacefully. No sudden breaks, and no fast corners. Also, I wont recommend you to sit near the front of the bus. It is 1.5 hrs of the best napping time.
[TODO: will come back to this later.]