
I'm definitely no expert but I do watch some sumo every so often. And Onosato has just made history, being promoted to Yokozuna, something that has only happened 75 times in sumo history.
Sumo works kinda like European soccer, with different divisions and teams/wrestlers getting promoted or demoted depending on their record.
Anytime someone gets promoted to Yokozuna it is a Big Deal, but this time especially so because Onosato is Japanese. Recently, most of the top sumo wrestlers have been Mongolian, and the only other current Yokozuna is Mongolian, so later this year when Onosato and Hoshoryu have their match, it will be huge.