Sumo in December (Tokyo or Kyoto)?

Greetings,

I'll be visiting Japan for three weeks in December. During this time, I'll be in Tokyo for one week and Kyoto for one week.

I'd like to see some sumo wrestling. Is there anywhere in Tokyo or Kyoto that would have sumo matches in December? It seems December is off season and my searching has turned up nothing.

No tournament is held in December.
Sumo tournaments are held 6 times a year, each 15 days, in January(Tokyo), March(Osaka), May(Tokyo), July(Nagoya), September(Tokyo) and November(Fukuoka).

See the article of this site:
http://www.japan-guide.com/e/e2080.html

As you have discovered there is no tournament in December. You might be able to visit a heya & watch Morning training session, see here (not my link) https://blog.gaijinpot.com/how-to-watch-a-sumo-morning-training-sessio...

No Grand Sumo Tournament.
But you can see the local area tour games(calling "巡業/jungyo") at Kyushu(far west fr Kyoto).
http://www.sumo.or.jp/EnJungyo/schedule
http://www.sumo.or.jp/Jungyo/schedule
Click each 詳しくはこちら(details here).
Use Google translate.
Already most good seats are sold out.