Non-touristy areas in Kanto

Hi

I will be in Tokyo from 14-25 Dec, and it's my 4th time.

My itinerary is as follows:

15-18 Dec Tokyo (work)
19-22 Dec Free
23-24 Dec Yuzawa
25 Dec Return home

Originally I had booked 19-20 Dec for Hakone, however, I would like to explore not so touristy areas of Kanto. Since I will be going to Yuzawa I am toying with the idea of getting a 5-day JR East Pass.

Any suggestions on areas to visit? Was thinking of Aomori and Sendai but not sure if the season is right?

Also, I need to be back to Tokyo on 22 Dec to meet 2 friends and go to Yuzawa together. Which means essentially if I use the 5-day pass, I would need to start the travel from Tokyo on 20 Dec.

For a few days, places worth considering between Tokyo and Sendai are Nikko, Aizu-Wakamatsu and Kitakata. In Aizu-Wakamatsu, you can do side-trips to the lovely village of Ouchijyuku or beautiful Inawashiro-ko which is full of swan in winter months. From Sendai you can do side-trips to popular Matsushima and Yama-dera. Time allowed, you can go further north to Hiraizumi with serene Motsu-ji and Chuson-ji.