Kosei Tanaka

As of November 2019, Tanaka is ranked as the world's best active flyweight by The Ring magazine, BoxRec and the Transnational Boxing Rankings Board.

Tanaka balanced professional boxing with school and in 2019 graduated with a degree in economics from Chukyo University. He is the cousin of Japanese figure skater Yuhana Yokoi and younger brother of amateur fighter Ryomei Tanaka.

Tanaka's second defense took place in September 2017 against little-known fighter Palangpol CP Freshmart. Tanaka was a huge favorite going into the fight, but Palangpol would prove to be Tanaka's toughest challenger so far, dropping the defending champion once in the first round and trading back-and-forth combinations for the rest of the bout. After a thrilling fight, Tanaka would finally gain the upper hand in round 9, as he knocked down Palangpol and continued to land big combinations as the challenger struggled to connect. Eventually, the referee stepped in and stopped the fight at 1:52 in round 9.

In December 2017, Tanaka vacated his junior-flyweight title to move to the flyweight division. In September 2018, Tanaka defeated Sho Kimura to equal Vasyl Lomachenko's record of becoming a three-weight world champion in just 12 fights.

In December 2016, Tanaka challenged former minimumweight title holder Moisés Fuentes for the WBO junior-flyweight title. Tanaka dominated Fuentes, dropping him in round five before referee Raul Caiz Jr stopped the fight, giving Tanaka a TKO victory. With the win, Tanaka became a two-weight world champion in just eight fights. Tanaka's first defense came against prospect Ángel Acosta. The former won a wide unanimous decision (117-110, 117-110, 116-111) and dropped Acosta once. Acosta had won all 16 of his previous fights by knockout.

As a child, Tanaka suffered from Legg–Calvé–Perthe disease. Despite this, he took up boxing and won four national tournaments competing as an amateur in the light flyweight division. At the continental and international level he was a quarter-finalist at the 2012 AIBA Youth World Championships and a silver medalist at the 2013 ASBC Asian Confederation Youth Boxing Championships.

Tanaka turned pro at the age of 18 in 2013. In November 2014, Tanaka defeated previously unbeaten Ryuji Hara by round 10 TKO to win the OPBF minimumweight title. In his next fight, Tanaka decisioned Julian Yedras (117-111, 117-111, 115-113) to win the WBO minimumweight title. Tanaka holds the Japanese record for winning a world title in the fewest fights (five), surpassing the previous record held by Naoya Inoue of six fights. Tanaka's only title defense at minimumweight came against Vic Saludar, whom he knocked out in round six after a left hook to the body. Saludar knocked down Tanaka in round six, and was ahead on all scorecards prior to the stoppage.

Kosei Tanaka (田中 恒成 , Tanaka Kōsei, born June 15, 1995) is a Japanese professional boxer. He is a three-weight world champion, having held the WBO flyweight title since 2018. He previously held the WBO minimumweight title from 2015 to 2016, and the WBO junior-flyweight title from 2016 to 2017. Upon winning his first world title in only his fifth bout, he became the fastest Japanese fighter ever to become a world champion. Along with Vasyl Lomachenko, he is also the fastest ever fighter to win titles in three weight-classes, having accomplished the feat in only 12 bouts.