The museum features a single room with various Sumo related objects and portraits of previous champions. Quite small and will take you only 15-30 minutes, however the entrance is free. A fun addition if you are attending one of the Sumo tournaments hosted in the arena where the museum is located. The tournaments take place in January, May and September. You could also quickly drop by when visiting the Edo-Tokyo museum, which is only a 5 minute walk away. Otherwise I would not bother coming here just for the Sumo museum alone.