Head to north. Snow will be beautiful!
Karuizawa is reachable from Tokyo by Shinkansen about an hour. You should be able to see the beautiful snow scenery there :)
There is a ski mountain as well if you like skiing.
The most famous spot in Chiba, Tokyo Disney land,
(By the way it is funny cuz Disney land is located in Chiba but it calls Tokyo Disney land.)
There are lots of super fun attractions, you can really enjoy.
As you know, you can find Mickeymouse in some area,
I recommed Kamakura.
Kamakura has many famous temples and buddha statues. Because about 800 years ago, Kamakura was the capital of Japan.
I recommend Kawagoe in Saitama too. The citiy call "Ko Edo".That meaning is little Edo. There are old style shops.
If you are into japanese food, There are lots of delicious restaurants within Tokyo so it is fun too stay in Tokyo and explore.
That's so nice you are spending new year holidays in Japan. How about participating a new year event, Hatsumode?
Hatsumode literally means "the first visit to shrines/temples" and we Japanese visit shrines or temples on the New Year's Day to wish for the luck in the new year.
Naritasan in Chiba prefecture (close to Narita Airport) is famous as the Hatsumode destination. You can experience Japanese cultural ritual of New Year holidays :)