The restriction upon entering Japan due to COVID-19 has been lifted (as of October 11, 2022). The visa exemption policy is the same as before the pandemic. See the page of the Ministry of Foreign Affairs of Japan for more detailed official information.
Participants are asked to book a hotel by themselves. Ochanomizu University is close to the Myogadani station (M23) of Marunouchi Line. The subway map can be downloaded from here. It would be convenient to stay at hotels along this line, e.g. Ikebukuro (M25), Korakuen (M22), Ochanomizu (M20), etc.