3 hours ago, Bumpkin said:
Ozumo, in fact, has three very different "formulas" or formats. The first format is for the top 16 or so Makuuchi rikishi. They, more or less, do a 15 day round robin. The Yokozunae face the Komusubisandthe Maegashiras in the first week.Then they face the Sekiwakes andthe Ozekis. They face each other at the end. The top 4 rikishi usually do a round robin on Days 13, 14 and 15. The second format is for the bottomof Makuuchi and all of Juryo. They face rikishi of similar rank for the first 8 to 10 days, then they face rikishi with similar W-L records at the end. The third format is for the 4 lower divisions. They face rikishiwith the same number of wins. As the basho goes on the rank disparity increases. Occasionally, a Makushita or Jonokuchi rikishi will have an 8th match. This is because they might have an odd number of rikishi competing.
This is an extremely concise and almost completely accurate description. It's much better than I would say because there would be no way I could be that concise, wanting to get in every single last bit of information.
There are a few things that can be added:
In general, the round-robin at the top is only (nearly) absolutely necessary for the sanyaku, and typically the sanyaku all face both M1 and M2 rikishi as well. The maegashira in the top 16 generally will meet each other less often than other maegashira of ranks close to each other would. The sanyaku round-robin is planned so that there are about the same number of matches with 2 sanyaku rikishi each day, with one more later in the tournament than at the beginning depending on the numbers they need to make. People withdrawing changes the calculation, and each time they have to rethink how they're going to do the intra-sanyaku matches for the rest of the tournament. They will almost always have the top 6 ranked rikishi face each other on Day 15 as the last 3 bouts of the regular schedule, generally 1v2, 3v4, 5v6, but with withdrawals they may end up doing something else or even scaling back to just the top 4. There's a special ceremony right before those last three matches, the sanyaku soroibumi, and there are some extra "prizes" given in each of those matches - a bow, a string, and arrows, though I don't think in that order.
The sekitori torikumi decision-making process has plenty of judgement involved in it, but there is almost none in the the lower divisions. They go down from the top pairing adjacently ranked rikishi with the same record, skipping over matches that are not allowed. It's really easy to figure out the first two rounds, though later rounds you always have to worry about checking to see if the match has already been held. The few things that are not predictable are those that deal with the edges of the schedule. They are: the crossover bouts between Juryo and Makushita (except for the first few each tournament necessitated by an odd number of sekitori competing), the pairing of the 6-0s (and sometimes 0-6s) due to large rank differences between adjacent ones making them shy away from the mechanically determined pairing, and the pairing in Jonokuchi to deal with odd numbers of rikishi of each record being present.
The lower divisions are contested in 7 Rounds, with the last taking place the last 3 days instead of over 2 like the others. If there are an odd number of rikishi to be paired for a Round, someone in Jonokuchi instead doesn't have a match and they try to make it up later. If at the end of the tournament there would be an odd man out, then someone at the bottom gets an extra match. Likewise, if a sekitori withdraws after Day 13 and creates one less rikishi available for Sekitori matches by not being on the torikumi Day 15, then they'll need to bring up someone from Makushita for an 8th match since they had already scheduled all the Round 7 matches before Day 13. That rikishi will generally be 2-5 or worse; one time recently it went quite a ways down the banzuke into Makushita as all the ones doing poorly near the top had withdrawn. In both cases, a win helps their next ranking, although a 3-5 is not as good as a 3-4, but a loss does not hurt it, so a 2-6 is the same as a 2-5.
