By air:
The primary international airports in Tokyo are:

• Haneda Airport (Code HND), around 18 km south of Tokyo Station and 25 km of Waseda University.
• Narita Airport (Code NRT), around 68 km east of Tokyo Station and 75 km of Waseda University.

From the airports to Waseda University, see here.

In the city:
More information about public transportation in Tokyo can be found here.