The workshop will be held at Koshiba hall, School of Science, the University of Tokyo. It is located in the Hongo campus, the main campus of the University of Tokyo, near Ueno.
Information to access the venue is found here. The hall is on the second floor of the Faculty of Science Bldg.1. The building is located just behind of Yasuda Auditorium, the symbolic building of the University.
It is 10-15 min walk from several subway stations, Nezu (Chiyoda-line), Hongo-san-chome (Marunouchi-line, Oedo line), and Todai-mae (Namboku line).
From Ueno-station, there is bus in the daytime, but it is not in operation before 9am on Sunday. It is probably safe to take a taxi, although it is 20-25 min walk if you don't get lost.
You may put "Yasuda Auditorium" as the destination if you use Google Map etc. to find the way. The venue (Faculty of Science Building 1) is the building seen behind the auditorium in this picture.
To those who will attend the Hyper-Kamiokande Collaboration meeting: It is NOT in the Kashiwa campus where HK meeting is held. See the railway map here. It takes ~40 min to go from Nezu station (subway Chiyoda-line) to Kashiwanoha Campus station (Tsukuba Express). The workshop will be finished around 11:00 on Monday, so that people can go to Kashiwa campus in time for the session in the afternoon.