Yes, I was also going to suggest looking on meetup.com for the Tokyo area and attend some events to meet other people with similar interests. Couchsurfing also has a Tokyo forum where you can try and meet other travelers and locals who like to meet visitors. There are often posts from other people in town looking for something to do.

Since you have so much time in the area, I would also suggest going to the seaside around Enoshima/Kamakura as a daytrip. Although like most places this would be much more fun if you're with someone else. Traveling alone is not for everyone, and it can be more interesting to be with other people even if it's just in a park or cafe instead of some specific tourist attraction.