You can book your accomodation through this page.
There you find a list of hotels next to the conference location at Kashiwa-no-ha Campus and in Kashiwa.
The rooms are blocked for you until end of registration deadline (Sept 20).
From Kashiwa Station it will take you 15 min to reach the conference place.
If you look for accomodations by yourself, it is convenient to book something along the Tsukuba Express Line, which brings you directly to the conference location at Kashiwa-no-ha Campus.
Popular and convenient areas are Akihabara or Asakusa.
From Akihabara or Asakusa Tsukuba Express Station it will take you 30 or 25 min to reach the conference place, respectively.