After his promotion, Kotoōshū was somewhat restricted by a knee injury.
He was also criticised for relying too much on the henka technique– jumping to the side at the initial charge.
It is not considered to be a move worthy of someone at his high rank.

Kotoōshū managed only three double-figure scores in 2006, and none at all in 2007, only doing enough to maintain his rank.
Shortly before the November 2007 tournament he dislocated his right knee in training.
Clearly troubled by the injury he pulled out on the 7th day, the first time in his career that he has had to withdraw from a tournament.
He preserved his ōzeki rank with a 9–6 score in January 2008.
In the Osaka tournament of March 2008 he injured his left arm in a match with Kakuryū on the 4th day and withdrew on Day 9 with only two wins.
There was speculation that he would be demoted to sekiwake in the following tournament in May.
Needing eight wins to hold his rank in the May 2008 tournament, he won 12 consecutive bouts including dominating victories against yokozuna Asashōryū on the 11th day and yokozuna Hakuhō on the 12th day.
He was easily defeated by Aminishiki on the 13th day, but came back strong to defeat Ama on the 14th day, becoming the first European to win a top division championship.
His father was in the crowd to witness his victory.
He was also congratulated by the Bulgarian President Georgi Parvanov.

Kotoōshū was unable to follow up his victory with a push for yokozuna promotion, producing scores of only 9–6 and 8–7 in the next two tournaments.
In October 2008 he denied allegations by disgraced former wrestler Wakanohō that he had thrown matches against Kotoōshū in return for money, saying "I am saddened by this.
It is all lies."
Wakanohō subsequently retracted his comments.
He produced scores of 10–5 in the first two tournaments of 2009, the best record amongst his fellow ōzeki.
In the May 2009 tournament, he finished the tournament with a 9–6 score.
However, he ended yokozuna Hakuhō's 33-bout winning streak on the 14th day.
In July 2009 he was in contention for the yūshō until the final day and finished runner-up with an impressive 13–2 score.
He never won more than ten bouts in a tournament after that.
He pulled out of the May 2011 tournament on Day 11, citing a knee injury.
He returned in July and preserved his rank by securing his eighth win on Day 10 (the last bout of fellow ōzeki Kaiō's career), finishing on 9–6.
However he withdrew once again in September after suffering five defeats in the first six days.

In the May 2012 tournament Kotoōshū withdrew with an ankle ligament injury on the last day, handing opponent Tochiōzan his twelfth victory by default and eliminating Hakuhō and two maegashira from the yūshō race.
The crowd showed their displeasure by booing as his withdrawal was announced.
He continued to suffer from injury problems, also withdrawing from the September 2012 as well as the March, September and November 2013 tournaments.
After his promotion, Kotoōshū was somewhat restricted by a knee injury. He was also criticised for relying too much on the henka technique– jumping to the side at the initial charge. It is not considered to be a move worthy of someone at his high rank.
Kotoōshū managed only three double-figure scores in 2006, and none at all in 2007, only doing enough to maintain his rank. Shortly before the November 2007 tournament he dislocated his right knee in training. Clearly troubled by the injury he pulled out on the 7th day, the first time in his career that he has had to withdraw from a tournament. He preserved his ōzeki rank with a 9–6 score in January 2008. In the Osaka tournament of March 2008 he injured his left arm in a match with Kakuryū on the 4th day and withdrew on Day 9 with only two wins. There was speculation that he would be demoted to sekiwake in the following tournament in May.
Needing eight wins to hold his rank in the May 2008 tournament, he won 12 consecutive bouts including dominating victories against yokozuna Asashōryū on the 11th day and yokozuna Hakuhō on the 12th day. He was easily defeated by Aminishiki on the 13th day, but came back strong to defeat Ama on the 14th day, becoming the first European to win a top division championship. His father was in the crowd to witness his victory. He was also congratulated by the Bulgarian President Georgi Parvanov.
Kotoōshū was unable to follow up his victory with a push for yokozuna promotion, producing scores of only 9–6 and 8–7 in the next two tournaments. In October 2008 he denied allegations by disgraced former wrestler Wakanohō that he had thrown matches against Kotoōshū in return for money, saying "I am saddened by this. It is all lies." Wakanohō subsequently retracted his comments. He produced scores of 10–5 in the first two tournaments of 2009, the best record amongst his fellow ōzeki. In the May 2009 tournament, he finished the tournament with a 9–6 score. However, he ended yokozuna Hakuhō's 33-bout winning streak on the 14th day. In July 2009 he was in contention for the yūshō until the final day and finished runner-up with an impressive 13–2 score. He never won more than ten bouts in a tournament after that. He pulled out of the May 2011 tournament on Day 11, citing a knee injury. He returned in July and preserved his rank by securing his eighth win on Day 10 (the last bout of fellow ōzeki Kaiō's career), finishing on 9–6. However he withdrew once again in September after suffering five defeats in the first six days.
In the May 2012 tournament Kotoōshū withdrew with an ankle ligament injury on the last day, handing opponent Tochiōzan his twelfth victory by default and eliminating Hakuhō and two maegashira from the yūshō race. The crowd showed their displeasure by booing as his withdrawal was announced. He continued to suffer from injury problems, also withdrawing from the September 2012 as well as the March, September and November 2013 tournaments.
Kotoōshū Katsunori