The Aki Basho Grand Sumo Tournament is going on right now in Tokyo. It will end next Sunday and the wrestlers will then have a break in schedule so you will not even have access to a touring regional event. Tough timing. If you arrive before Sunday, you can at least watch the action on TV. It is broadcast from 4:00 to 6:00 pm on NHK. For the closing day on Sunday, it will run a bit longer to include the award ceremony.
I second the advice to change your stay to Kyoto, which is very near Osaka. If you can't change, at least make plans to ride the train into Kyoto for a daytrip or two during your stay. Another day can be very well spent on a daytrip to the other nearby ancient city of Nara.