Sports season is coming in Japan now !
You would be able to have exciting moments with lots of sports in western Tokyo Tama area as well !
The biggest sport facility is Ajinomoto Stadium in Tokyo Chofu city, with the easy access by about 30 minutes only from Shinjuku station by Keio line.
Mainly Soccer and Football games are held in this season there.
For American football, Kantoh Collegiate Football matches are held at Aminovital Field, located just next to Ajinomoto Stadium and let's try to visit there if you are interested !
Football Match schedules : http://www.kcfa.jp/schedule_league/ (Japanese)
Event schedules at Ajinomoto Stadium, Aminovital field, Truck field, etc :
http://www.ajinomotostadium.com/schedule/ (Japanese)
Access information to Ajinomoto Stadium :
http://www.ajinomotostadium.com/english/access.php (English)