Kazuto Ioka

• 16th All Japan Selected High School Boxing Championships, Light flyweight Tournament winner (2005)
• 17th All Japan Selected High School Boxing Championships, Light flyweight Tournament winner (2006)
• 59th Inter-highschool championships, Boxing, Light flyweight Tournament winner
• 60th Inter-highschool championships, Boxing, Light flyweight Tournament winner
• 60th National Sports Festival, Boxing, Boys, Light flyweight Tournament winner
• 61st National Sports Festival, Boxing, Boys, Light flyweight Tournament winner
• 62nd National Sports Festival, Boxing, Adult, Light flyweight Tournament winner
• 63rd National Sports Festival, Boxing, Adult, Light flyweight Tournament winner

Upon failing to qualify for the Olympics, Ioka dropped out from college and turned professional in 2009. On April 12, 2009, he fought against Thongthailek Sor Tanapinyo, and won his debut via a third-round technical knockout. After this victory, he won six straight victories. After winning 5 fights, Ioka competed for the vacant Japanese light flyweight title. Ioka captured the national title by stopping Masayoshi Segawa in the final 10th round.

On his next fight, Ioka won the WBC minimumweight title from Thai Oleydong Sithsamerchai via a fifth-round technical knockout in the latter's seventh title defence at the World Memorial Hall, in February 2011. Sithsamerchai was knocked down twice over the course of his first professional loss. Ioka went on to defend his title against Juan Hernández, winning via unanimous decision (118-111, 117-111, 116-112).

After one further defense, Ioka met WBA champion Akira Yaegashi in a match that marked the first time two Japanese fighters had met to unify world titles. The fight took place on 20 June 2012 at the Osaka Prefectural Gymnasium. Ioka defeated the WBA champion Akira Yaegashi via a unanimous decision (115-113, 115-113, 115-114). The two fighters exchanged hard shots throughout a tense, tactical fight. The fight ended with Yaegashi and Ioka trading combinations while looking for a knockout. From early in the fight, Yaegashi's eye was nearly shut. The ringside doctor performed several checks on it but Yaegashi was allowed to finish the fight.[3][4][5] When asked whether the result would have been different unless he got swollen eyes, Yaegashi said "We should not think about it. There is no if's in boxing".[6] The day after the fight, Ioka decided to move up a weight division.[7][8]

Shortly after the fight, Ioka moved up to light flyweight as well. On December 31, 2012, Ioka beat undefeated José Alfredo Rodríguez for the vacant WBA (Regular) light-flyweight title at the Osaka Prefectural Gymnasium. Ioka knocked Rodríguez down once in round 1 and twice in round 6 before the referee stopped the fight.[9] Ioka held the Regular version of the WBA's title, while Román Gonzalez was the WBA (Super) champion.[10] Ioka went on to defend his title three times but he never faced González.

On February 28, 2014, Ioka would vacate the WBA title to move up to the flyweight division in order to attempt becoming a three division world champion.[11] On May 7, 2014, Ioka faced Thai IBF champion Amnat Ruenroeng at the Osaka Prefectural Gymnasium. Ioka seemed to be the more active boxer but Ruenroeng landed heavier blows while countering Ioka. Ruenroeng lost a point for hitting after the break. Nevertheless, Ruenroeng retained his title with a split decision (119-108, 115-112, 113-114).[12] The 119-108 card turned in by judge Pawel Kardyni was criticized as being far too wide.[13]

On April 22, 2015, Ioka realized his goal to be a triple champion, when he defeated WBA (Regular) champion Juan Carlos Reveco by majority decision (116-113, 115-113, 114-114). The fight saw Reveco take the early rounds but Ioka came on strong in the middle rounds and got the nod in the end.[14] Reveco appealed the decision to the World Boxing Association, who ordered an immediate rematch.[15] Ioka was later granted a voluntary defense against Roberto Sosa, with the winner ordered to face Reveco.[16] Ioka beat Sosa in a shutout unanimous decision (120-108, 119-109, 119-109). The Ioka-Reveco rematch was set for December 2015. Ioka outworked Reveco at the start of the match. However, Reveco started rallying in round 7. Ioka answered in kind, nearly knocking out Reveco. Reveco finally went down in round 11 following a series of hooks to the body.[17]

Ioka was nearing a deal to fight WBA (Super) flyweight champion Juan Francisco Estrada, when the latter vacated to compete at super flyweight.[18] Ioka was knocked down for the first time in his career against 18 year old challenger and WBA interim champion Stamp Kiatniwat. Ioka rallied, pummeling Kiatniwat to the body, until he finally dropped the challenger twice in round 9. The referee halted the fight with the second knockdown. The win was Ioka's fourth flyweight defense.[19]

In November 2017, Ioka vacated his title after five successful defenses. He was planning to defend on December 31 but his father stated that he would not be ready to do so, as he hadn't kept up with his training after getting married earlier in the year to Nana Tanimura.[20][21] Ioka went on to announce his retirement at age 28 after getting married and reportedly falling out with his father and promoter, Kazunori Ioka.[22]

On New Year's Eve in 2018, Ioka fought Donnie Nietes for the WBO junior bantamweight title in an attempt to win a world title in a fourth weight class. Ioka, however, lost by split decision.