Ideas for for last 2 days

First trip abroad in many years. Guy in his mid 30s The first 14 days i'll be with a group the last 2 figuring out what to do.

We will be spending 6 days in tokyo, 3 in nagoya, 4 in osaka , another in kyoto and some day trips to takayama, nira, uji, kobe and some other locations around there.

The 2 days I have free I'll be leaving from Tokyo and coming back there the 2nd day at night. I want to see as much as I can but don't want to be overwhelmed with tons of and tons of travel and stops so was thinking of one place to go. Any ideas?

What are your interests?
Nature?
Theme parks?
Museums?
Traditional Japan?
Onsen?
Party?
Hikking?
…

There are simply too many places close to Tokyo to recommend without an idea what you are interested in. Specially considering you spent the rest of the trip with a tour group, so no/limited flexibility of what you can decide by yourself, for those 2 days, your innermost desires should come first.