Gakuensai, or student festivals, are held at universities all over Japan. The annual festival at the University of Tsukuba is called "Sohosai". This is a good chance to visit the University and interact with students.
There are lots of events, performances, food, and other festivities. Parking should be tight, so coming by bicycle is probably adviseable.
Those of you interested in traditional Japanese warrior arts might like to watch the demonstration by Kashima Shinryu. Student members will perform in front of Matsumi pond in the middle of the campus each day of the festival. (The demonstration starts at noon or 12:30.)
See also: University of Tsukuba