There is a ranking system in professional sumo. The title of the top ranker is Yokozuna. When Ozeki (title of the second ranker) ranked wrestler won in the last 2 tournaments, he can be promoted to the Yokozuna. Conversely, Yokozuna who regretted his achievement in the last 2 tournament, he is forced to retire.
Yokozuna is not limited to one person, sometimes there are several yokozuna at one time. In Kyushu tournament of November 2017, four people, Hakuhou（白鵬）, Harumafuji（日馬富士）, Kakuryu（鶴竜） and Kisenosato（稀勢ã®é‡Œï¼‰ were the yokozuna.
Also, high dignity is required for the Yokozuna. Therefore, if the Yokozuna causes a scandal he will be forced to retire, even if his grades are good. Harumafuji retired after this year’s Kyushu tournament, because he caused a problem hurting the young wrestler during drinking.