
A mono-ii.
A mono-ii is the discussion held by shimpan when the gyoji's decision for a bout is called into question. Technically, the term refers to the querying of the decision: the resulting discussion is a kyogi.
Overview[]

Head shimpan presenting the audience with the result of the match.

Yokozuna Hakuho raising his hand indicating for a mono-ii.
A mono-ii occurs when the gyoji makes a questionable decision regarding the outcome of a match. One or more shimpan would raise their hand inferring that they want to discuss about the gyoji's decision. At this time, the head shimpan would contact other shimpan in the video room. The gyoji would always have to give their side and why they committed the choice they did. In the picture (on the left), you can see the head shimpan communicating with the shimpan in the video room. Once the discussion is over, the head shimpan would tell the audience the result of the match though a microphone. The outcome of the match can either be a gunbai-dori (The decision following a mono-ii affirming the gyoji's original decision), gyoji gunbai sashichigae (the decision following a mono-ii reversing the gyōji's original decision.), or a torinaoshi (rematch).
A unique rule applies that sumo wrestlers can call for a mono-ii if they also don't agree with the call. This happens very rarely, but a notable case happened on the May, 2014 tournament, day 12, where yokozuna Hakuho raised his hand claiming that ozeki Goeido pulled yokozuna Kakuryu's hair (which is not allowed). This proved to be the case, after replays distinctly show Goeido's hand pulling Kakuryu's hair.
Notable Controversial Calls[]

Shikimori Inosuke insisting and trying to prove that his call to Tochinishiki was the correct one while the dohyo judges favored Kitanonada.
September 1958 Day 1: The 19th Shikimori Inosuke (highest ranked gyoji) referreed a bout between Tochinishiki & Kitanonada, the result of which was disputed and overturned by the judges. Gyoji are obliged to yield to the final decison of judges, but Inosuke was adamant and heatedly upheld his call for a full ten minutes. He did, however, relent, and accepted the defeat. He was then suspended for the rest of the tournament, but it is said that he never doubted his original decision. Later photo and video proof, proved that the Shikimori Inosuke was correct (or at least a torinashi should have been enforced). Shikimori Inosuke was suspended indefinitely, but to public outcry, his suspension was cut short to 12 days.

Photo evidence clearly showing that Toda's feet was outside.
March 1969 Day 2: Yokozuna Taiho was wrestling a match against rank-in-file wrestler, Toda. Toda pushed Taiho to edge of the dohyo before Taiho slapped down Toda. They both went out tumbling simultaneously. The gyoji awarded Taiho, the win, but a mono-ii was called. The gyoji's decision was overruled. Later photo and video evidence showed that Toda's feet touched outside the dohyo, before Taiho's. This was met with public outcry as this decision ended Taiho's 45 match winning streak. This caused such a furor that video replays were introduced after the incident.

Instant slow motion replay show that Tochinoshin's heel is not out.
May 2019 Day 13: Former ozeki, Tochinoshin was wrestling against maegashira Asanoyama. Tochinoshin was pushed to the edge, but was able to regain himself and pull Asanoyama down. The gyoji awarded Tochinoshin with the victory, but a mono-ii was called. The head shimpan (former sekiwake Masurao) claimed that Tochinoshin's heel was out so they rewarded Asanoyama with the victory. With photo and video evidence, Tochinoshin's heel was clearly not out and viewers were enraged with the decision. What angered the viewers even more, was that Tochinoshin was trying to regain his hard-earned ozeki rank and was one win away, but since he lost he had to win another match (he later retained his ozeki rank). Asanoyama ended up getting the yusho. Many speculate that since Donald Trump was visiting and was going to present the President's Cup to the winner, the Japan Sumo Association gave the match to Asanoyama, so Donald Trump could present the cup to a Japanese-born instead of a foreigner (gaijin). The chairman of the Yokozuna Deliberation Council criticized the head shimpan (former sekiwake Masurao), and he later gave up his judging duties, citing high blood pressure and left the sumo association all together a couple months later.