Sanctuary | Official Trailer | Netflix

If you want to get some information about Sumo in a entertaining way I'd like to propose you watch the Netflix show Sanctuary in which you follow one guy who joins the sport and you see a lot of behind the scenes of the sport how they train, how the politics between the stables works, etc. and obviously also how the sport actually works in the ring.

Synopsis:

The series portrays a rookie wrestler, Enno, a debt-ridden delinquent who lives in violence and with a broken family, as he tries to make his way in the world of professional sumo. As he is scouted by the master of Ensho stable for his talent and physique, and climbs the ranks only for the money with no interest for sumo, he becomes the target of criticism from the sumo executives for his over-the-top personality and his lack of respect for the traditions of the sport.

It isn't a documentary but a drama TV show but that is also what makes it easier to watch even with people who normally would not be into Sumo like one's partner for example.