Kaiō Hiroyuki (born 24 July 1972 as Hiroyuki Koga) is a former professional sumo wrestler from Nōgata, Fukuoka, Japan.
He made his debut in 1988, reaching the top makuuchi division in 1993. He held the second highest rank of ōzeki or champion for eleven years from 2000 to 2011, and is the longest-serving ōzeki of all time in terms of number of tournaments fought.
In his career, Kaiō won five top division yūshō or tournament championships, the last coming in 2004. This is the modern record for someone who has not ultimately made the top rank of yokozuna. He was a runner-up in eleven other tournaments, and also won 15 sanshō or special prizes, the third highest ever.
In November 2009 he broke the record previously held by Takamiyama for the most tournaments ranked in the top division, and in January 2010 he surpassed Chiyonofuji's record of most top division bouts won. In the May 2010 tournament he became the only wrestler besides Chiyonofuji to reach one thousand career wins, and he surpassed Chiyonofuji's career wins record of 1045 in July 2011. He retired in the same tournament to become a coach at Tomozuna stable under the elder name Asakayama. In 2014, he established the latest incarnation of the Asakayama stable.
Koga did karate for two years in elementary school, and judo in his second year of junior high school. He had not shown much interest in sumo but was asked by his parents to take part in sumo competitions. It was at one such competition in Fukuoka that he was spotted by the wrestler Kaiki, later Tomozuna Oyakata. After being introduced to Kaiki by a common acquaintance in Nōgata, the young Koga was recruited to Tomozuna stable upon graduation from junior high. Kaiki thought so highly of the apprentice that he promised Koga's parents that he would become a sekitori by the age of 20. However, because the move had been set up by others around him, and he had not ever had the ambition to be a rikishi himself, Koga initially had doubts that he would be able to succeed in sumo.
He made his professional debut in March 1988, at the same time as former yokozuna Akebono, Takanohana and Wakanohana, who all made the top division faster than him but who had all retired by 2003. Initially fighting under his own surname, he reached the makushita division in September 1990 after winning the sandanme championship with a perfect 7–0 record. He won the makushita tournament in July 1991 and in November 1991, in his hometown tournament in Kyushu, he earned promotion to the sekitori ranks—a performance he later recalled as one of his most memorable ever. Upon making his debut in second highest jūryō division in January 1992 he adopted the shikona of Kaiō. After a few injury problems he worked his way up the jūryō division and reached the top makuuchi division for the first time in May 1993. He fell back to jūryō after a 4–11 score in his makuuchi debut. This meant that, oddly, he had recorded a make-koshi or losing score in every tournament in which he was debuting in a new division. However, he returned to the top division in November 1993, where he was to remain for the rest of his career. After defeating his first yokozuna and winning his first special prize in March 1994, he was promoted to a san'yaku rank for the first time for the following tournament in May 1994, at komusubi. He made sekiwake rank in January 1995, and came through with a winning record and another prize in his sekiwake debut.
In the earlier part of his top division career Kaiō's lack of consistency, and injury problems, denied him the major promotion to ōzeki that his ability merited. He set records for both the number of tournaments spent at sekiwake (21) and for the longest run being consecutively ranked in the junior san'yaku ranks without making ōzeki (14). He also accumulated a record equalling ten Shukun-shō, or Outstanding Performance Prizes. Together with his five Kantō-shō, or Fighting Spirit awards, he has 15 special prizes in total, placing him third behind Akinoshima and Kotonishiki. He also earned six kinboshi or gold stars for defeating yokozuna when ranked as a maegashira. He twice took part in playoffs for the championship, in November 1996 (with four other wrestlers, won by Musashimaru) and in March 1997 (with three others, won by Takanohana). In May 1997 injuries to his left leg sustained in a match with Takanonami caused him to miss tournaments and took over a year to fully heal. He could not win more than eight bouts in a tourney during 1998, but he was runner-up in two more tournaments in 1999, in May and November.
Kaiō won his first top division tournament championship in May 2000 from the komusubi rank, defeating yokozuna Takanohana and three ōzeki and losing just one bout to Akebono. It was the first top division yūshō by a wrestler from Tomozuna stable since Tachiyama in 1916. He attributed his victory partly to cutting down on his beer consumption. Set a target of eleven wins by the Japan Sumo Association for promotion to ōzeki in the following tournament in July 2000, he achieved the necessary total on the final day and his promotion was confirmed a few days later. He was 28 years of age, and the 44 tournaments it took him to reach ōzeki from his top division debut was the second slowest ever. Nevertheless, he went on to maintain the rank for eleven years, eventually becoming the oldest ōzeki since the start of the Shōwa era in 1926, and also the longest serving, in terms of number of tournaments, a record he holds jointly with Chiyotaikai.
After becoming an ōzeki Kaiō won four more championships and came close to yokozuna promotion on a number of occasions. In March 2001 he won his second championship, losing only to the two yokozuna Takanohana and Musashimaru, and finishing on 13–2, one win ahead of them and Musōyama. His third yūshō came in July 2001, when in the absence of Takanohana he clinched the title on the fourteenth day by defeating Musashimaru. However he was denied the chance of going for consecutive yūshō because after each of these triumphs he had to withdraw from the following tournament with sciatica in his lower back, a chronic problem which continued to restrict his mobility for the rest of his career. He was three times a runner-up in 2002, and then after finishing runner up in consecutive tournaments in March and May 2003 he took the July championship, defeating his only rival Chiyotaikai on the final day to win the yūshō with a 12–3 record. However, after injuring himself in training he could win only seven bouts in the following tournament.
On 6 October 2001, JR Kyushu started a new train service named after him from Hakata to his home town Nōgata, making it one of the few JR trains named after a living person. Kaiō was also invited to the launching ceremony, but eventually did not attend because of his health issues.
In 2004, a year in which Kaiō was injury-free, he was runner-up in March, and then won the September tournament virtually unchallenged after two of his three ōzeki rivals dropped out injured and yokozuna Asashōryū could score only 9–6. He finished on 13–2, two wins ahead of rank-and-filers Tochinonada and Kyokushūzan. In the crucial following tournament in November, he dropped his opening bout to Kotomitsuki and then was surprisingly defeated by newcomer Hakuhō on Day 10 and sekiwake Miyabiyama on Day 12. Although he defeated Asashōryū on the final day to finish runner-up to the yokozuna with twelve wins, it was one win short of the thirteen deemed necessary by the Sumo Association for promotion. Kaiō was set another target of thirteen wins in the following January 2005 tournament, but pulled out with a shoulder injury on the 9th day. This proved to be his final attempt at yokozuna promotion. Due to his injuries he was kadoban (in danger of demotion from ōzeki) a total of thirteen times, a record second only to Chiyotaikai.
After his eleventh runner-up performance in November 2004 Kaiō seldom contended for the championship or even produced a score in double figures, leading some commentators to suggest his retirement was overdue. However, he continued to set records. His 8–7 mark in January 2008 was his 64th kachi-koshi (majority of wins against losses) in the top division, breaking the record previously held by Kitanoumi. In May 2008 he became only the fourth man, after Kitanoumi, Ōshio and Chiyonofuji, to reach 900 career wins, and in July 2008, on his 36th birthday, he moved ahead of Taihō into third place on the all-time list of top division wins, behind only Chiyonofuji and Kitanoumi. In September 2009 he won his 965th career match, moving past Ōshio into second place on career wins. The November 2009 tournament was Kaiō's 98th ranked in the top division, breaking the 25-year-old record held by Takamiyama. During this tournament he overtook Kitanoumi to move into second place on top division wins, just one behind Chiyonofuji on 806. He also became the first wrestler to post six successive 8–7 scores in a calendar year.