Koki Osaki

is a Japanese Muay Thai kickboxer, currently competing in the bantamweight division of RISE, where he is the incumbent RISE Bantamweight champion.

As of March 2023, he is ranked as the fifth best super flyweight (-55 kg) kickboxer in the world by Beyond Kickboxing and sixth best flyweight (-56.7 kg) by Combat Press.

Martial arts career Early career Osaki made his professional debut at J-NETWORK J-KICK 2016～Honor the fighting spirits～2nd with a unanimous decision victory over Idomu Tateshima. He amassed a 10-2-1 record, before fighting Satoshi Katashima for the WMC Japan Super Flyweight title at Muay Lok 2018 Challenge. Osaki won the title with a fourth-round TKO.

In his next fight, at J-KICK 2018～4th～, Osaki fought Masanori Matsuzaki for the J-NETWORK Super Flyweight title. He won the fight by unanimous decision. Hirayama won the fight by an extra round majority decision.

RISE Bantamweight Osaki faced Jin Mandokoro in his RISE debut at RISE 135 on November 4, 2019. He lost the fight by unanimous decision. Osaki faced Kazuya Okuwaki, in his second RISE appearance, at RISE 142 on September 4, 2019. He won the fight by a first-round knockout, flooring Okuwai with a high kick.

Osaki faced the third-ranked RISE bantamweight contender Kyosuke at RISE 145 on January 30, 2021. He won the fight by a second-round knockout. Osaki dropped his opponent with a low kick 30 seconds into the final round of the contest, which left his opponent unable to rise from the canvas.

Osaki faced Kaito Fukuda for the BOM Bantamweight title at BOM WAVE 04 on April 11, 2021. He won the fight by unanimous decision, with two scorecards of 49–48 and one scorecard of 49–47. After capturing his third professional championship, Osaki was booked to face Azusa Kaneko in a reserve fight of the 2021 RISE Dead or Alive Tournament, which took place on July 18, 2021. He won the fight by unanimous decision, with scores of 30–29, 30–29 and 30–28.

Osaki was scheduled to face Koudai Hirayama in a tournament reserve match at RISE WORLD SERIES 2021 Yokohama on September 23, 2021. The two fought previously on May 26, 2019, with Hirayama winning by an extra round majority decision. Osaki was later rescheduled to face Shiro in the tournament semifinals, as a short notice replacement for his brother Kazuki Osaki. He was later removed from the tournament, as he had missed weight by 3.2 kg.

Catchweight bouts Osaki was booked to face Tatsuto Ito at 57.5 kg for RISE 156 on March 27, 2022. He won the fight by unanimous decision, with all three judges scoring the bout 30–28 in his favor.

Osaki faced Yugo Kato in a 55.5 kilogram bout at the May 28, 2022, NO KICK NO LIFE event. He won the fight by a fourth-round technical knockout.

Osaki faced Jyosei at RISE 160 on July 29, 2022, in a 56 kg catchweight bout. He won the fight by a first-round technical knockout, after knocking Jyosei down three times by the midway point of the opening round.

Return to bantamweight Osaki faced Shiro at RISE World Series 2022 on October 15, 2022. They were initially expected to face each other in the semifinals of the 2021 RISE "Dead or Alive" bantamweight tournament, before the fight was cancelled due to Osaki missing weight. He lost the fight by unanimous decision, after an extra fourth round was fought.

Osaki faced Seiki Ueyama at RISE World Series / SHOOTBOXING-Kings 2022 on December 25, 2022. At the official weigh-ins, Ueyama missed weight by 1.5 kg, which resulted in him being deducted two points before the start of the fight and having to fight in bigger gloves. Osaki won the fight by unanimous decision, with one scorecard of 29–28 and two scorecards of 29–27.

Osaki faced Ryoga Terayama in the main event of RISE 165: RISE 20th Memorial event on February 23, 2023. The fight ended in a majority decision draw. Osaki landed an accidental low blow midway through the final round, which rendered his opponent unable to continue fighting and prompted the referee to call for a technical decision. The pair was booked to fight in an immediate rematch at RISE 168 on May 28, 2023. He won the fight by a second-round technical knockout.

Osaki faced Yugo Kato in a RISE Bantamweight title eliminator at RISE World Series 2023 - 2nd Round on August 26, 2023. He won the fight by unanimous decision, with scores of 30–29, 29–28 and 29–28.

RISE Bantamweight champion Osaki challenged Masahiko Suzuki for the RISE Bantamweight (-55kg) title at RISE 174 on December 10, 2023. He won the fight by unanimous decision, with scores of 50–47, 50–47 and 50–48.

Osaki was expected Aiman Lahmar at RISE 178 on May 19, 2024. Lahmar withdrew from the fight on May 7, due to knee and hip injuries, and was replaced by Samvel Babayan. Babayan was himself forced to withdraw with visa issues and was replaced by Yodbuadang 3rdplacegym.

Osaki made his first RISE Bantamweight (-55kg) title defense against Ryunosuke Omori at RISE 181 on August 31, 2024. He retained the title by way of unanimous decision, with scores of 49–47, 50–47 and 50–46. Osaki was able to knock his opponent down once, with a right straight in the opening round.

Osaki made his ONE Championship debut against Huo Xiaolong at ONE Friday Fights 86 on November 8, 2024. He won the fight by unanimous decision.

Osaki faced the former RISE featherweight champion Keisuke Monguchi in a bantamweight non-title bout at RISE Fire Ball on May 11, 2025. He won the fight by second-round technical knockout.

Osaki faced Djillali Kharroubi in a non-title bout at RISE 191 on August 30, 2025. He won the fight by unanimous decision.

Osaki faced Wuttikorn Suannamtankiri at RISE 193, on November 9, 2025. He won the bout via TKO in the third round, finishing Suannamtankiri with punches.

Osaki faced Shiro at RISE EL DORADO 2026, on March 28, 2026, in a rematch, this time for Shiro's RISE World Bantamweight (-55kg) Title. He won the bout via unanimous decision, dropping Shiro in round three.

Osaki made his Muay Thai return in his Rajadamnern World Series debut at RWS 200, on June 27, 2026. He faced Chaitone Wor. Auracha for the RWS Interim Super Bantamweight (122 lbs) Title. He won the bout via TKO in round one, knocking Auracha out with punches.

Championships and accomplishments Professional J-NETWORK 2018 J-NETWORK Super Flyweight Champion World Muay Thai Council 2018 WMC Japan Super Flyweight Champion Battle of Muay Thai 2021 BOM Bantamweight Champion RISE 2023 RISE Bantamweight (-55kg) Champion One successful title defense 2026 RISE World Bantamweight (-55kg) Champion

Rajadamnern Stadium 2026 interim Rajadamnern Stadium Super Bantamweight (122 lbs) Champion

Amateur 2013 Muay Thai Windy Super Fight -40 kg Champion 2014 All Japan Jr. Kick -45 kg Champion 2015 J-NETWORK All Japan A-league -53 kg Winner & Spirit Award

Fight record

Amateur record