The meeting will take place at the Hongo campus of the University of Tokyo. The closest international airports to Tokyo are Narita (NRT) and Haneda (HND).

Access map from airports to the campus.

From Nartita airport, the easiest way to get to the campus is to take the Keisei line train to Keisei-Ueno station, from where it is a short taxi ride or a pleasant 15 min walk to the campus. 
There are various options: the "Skyliner" is the fastest and most expensive (40 mins, JPY 2470 to Keisei Ueno station), the "Keisei Main line" trains slowest and least expensive (80 mins, JPY 1030), and the "Access Express line" somewhere in between.

Alternatively, you can take the Narita Express train to Tokyo station (60 minutes, JPY 3020). 

From Haneda airport, the easiest route is to take the Keikyu line to Shinagawa station, from where you take the JR Yamanote line to Tokyo Station. 
(Alternatively, take the Tokyo monorail from Haneda and transfer to the JR Yamanote line at Hamamatshucho Station, going to Tokyo Station.)

From Tokyo Station, take the Marunouchi metro line to Hongo-sanchome Station, from where it is a few minutes' walk to the campus. Tokyo station is rather large, so it can take time and perseverence to transfer between lines.

Information and maps for the Tokyo metro.

Train and metro timetable information in English.