Ryusei Kumagai

, better known by his ring name Ryusei, is a Japanese kickboxer. He currently competes in the featherweight division of KNOCK OUT, where he is the current ISKA K-1 Intercontinental Super Featherweight champion and the former KNOCK OUT Black Featherweight champion.

Kickboxing career KNOCK OUT Early career Ryusei made his professional debut against Naoki Iijima at Suk Wan Kingthong on April 7, 2019. He won the fight by a first-round knockout. Ryusei was next booked to face Shoi at REBELS 62 on August 10, 2019. He won the fight by a first-round knockout.

Ryusei made his debut with KNOCK OUT, the REBELS sister organization, against Miki Urabayashi at KNOCK OUT CHAMPIONSHIP.1 on February 11, 2020. He won the fight by a second-round technical knockout. Ryusei next faced Hiroto Sameshima at Suk Wan Kingthong Rookies on July 19, 2020. He won the fight by a third-round technical knockout.

Ryusei faced Yuki Chiba at REBELS 65 on August 30, 2020. He won the fight by a first-round knockout, after knocking Chiba down three times by the 1:59 minute mark of the opening round. Ryusei was then booked to face KotaroZLS at REBELS 69 on December 6, 2020. He knocked Kotaro out with a head kick, only 51 seconds into the fight.

Ryusei faced Takeru Owaki at KNOCK OUT ～The REBORN～ on March 13, 2021. He won the fight by unanimous decision, the first decision win of his professional career. One judge scored the fight 30–28 in his favor, while the remaining two judges awarded him all three rounds of the bout. Ryusei made his third KNOCK OUT appearance against Ryuta Inoue at KNOCK OUT EX 2021 vol.4 on August 22, 2021. He won the fight by a first-round technical knockout, forcing the referee to step in with a flurry of punches at the 2:00 minute mark.

Black Featherweight champion Ryusei's undefeated 8–0 run earned him the chance to fight Ginji for the inaugural KNOCK OUT Black Featherweight title at KNOCK OUT 2021 vol.5 on October 29, 2021. He utilized his height and reach advantage to win the fight by unanimous decision, with all three judges awarding him the first and the second round on their scorecards. Following this victory, eFight named Ryusei their October 2021 "Fighter of the Month". The fight was ruled a split decision draw after the first three rounds, with one judge scoring the fight 30–29 for Ryusei, while the remaining two judges scored it as an even 29–29 draw. An extra fourth round was contested, after which Ryusei was awarded the split decision.

Ryusei made his Rizin FF debut against Kaishi at Rizin 37 - Saitama on July 31, 2022. He won the fight by a third-round knockout, stopping Kaishi with a combination of a left hook and a flying knee.

Ryusei faced Yukinori Ogasawara at KNOCK OUT 2022 vol.5 on September 23, 2022. It was Ryusei's first fight following his departure from TRY HARD gym. Ryusei next faced Gu Taewon at KNOCK OUT 2022 vol.7 on November 19, 2022. He won the fight by a second-round head kick knockout.

Ryusei faced Dawsakorn Mor.Tassanai at INOKI BOM-BA-YE x Ganryujima on December 28, 2022, in a ganryujima rules bout, which was contested in MMA gloves and allowed for throws and chokes. Ryusei won by first round knockout with a left hook to the body only 31 seconds into the bout.

Ryusei was expected to face Yodkitsada Yuthachonburi at KNOCK OUT 2023 SUPER BOUT BLAZE on March 5, 2023. Yodkitsada withdrew on February 8 and was replaced by the Rajadamnern Stadium super bantamweight champion Petchsansab SorJor Tongprajin. The fight was ruled a majority decision draw after the first three rounds, with one judge scoring the bout 30–28 for Ryusei, while the remaining two judges scored it as an even 29–29 draw. Ryusei was awarded a unanimous decision, 10–8 on all three scorecards, after an extra round was contested.

Ryusei faced Qumuxifu in a -59 kg catchweight bout at KNOCK OUT 2023 vol.2 on June 11, 2023. The fight was ruled a unanimous decision draw, following the first three rounds, with three even scorecards of 28–28. Although Ryusei was able to win the second and third rounds 10–9 with all three judges, Qumuxifu was awarded a 10–8 in the opening round, as he was able to knock the champion down with a right hook. Ryusei was declared the winner by unanimous decision, after an extra fourth round was contested.

Ryusei faced Facu Suarez at KNOCK OUT 2023 vol.6 on December 9, 2023. He won the fight by a third-round knockout.

Ryusei was expected to face Kyo Kawakami at KNOCK OUT 2024 vol.1 on February 25, 2023. The bout was postponed for KNOCK OUT 2024 vol.2 on April 27, 2024, as Ryusei withdrew due to illness on February 23. The fight was reschedule for KNOCK OUT 2024 vol.2 on April 27, 2024. Ryusei won the fight by unanimous decision.

Ryusei was scheduled to face Kotaro Yamada at KNOCK OUT 2024 SUPER BOUT BLAZE on June 23, 2024. Yamada was replaced by Taimu Hisai due to injury and the bout was turned into a title fight for the inaugural Super Featherweight belt. Ryusei lost the fight by unanimous decision.

Ryusei vacanted the KNOCK OUT Black Featherweight title on 11 July 2024 in order to move up in weight.

Ryusei faced Braian Gavio for the vacant ISKA K-1 World Super Featherweight title at KNOCK OUT K.O CLIMAX 2024 on December 30, 2024. Ryusei won the fight by unanimous decision.

ONE Championship/KNOCK OUT On January 31, 2025, it was announced that Ryusei signed with ONE Championship and he made his debut against Suriyanlek Por.Yenying on March 23, 2025, at ONE 172. He won the fight via unanimous decision.

Ryusei challenged the KNOCK OUT Black Super Featherweight (-60kg) titleholder Taimu Hisai at THE KNOCK OUT on June 22, 2025. He lost the fight by majority decision following an extension round.

Ryusei faced Lom-Isan ReonGym at Kickboxing Fes. GOAT on October 30, 2025. He won the fight by unanimous decision, after knocking his opponent down in the third round.

Ryusei faced Shuhei Kumura at KNOCK OUT 60 on December 30, 2025. He won the fight by a second-round knockout.

Titles and accomplishments Amateur 2015 Wan Kingthong Real Champion -38kg Tournament runner-up 2017 WINDY Super Fight Kick -51kg Champion

Professional KNOCK OUT 2021 KNOCK OUT Black Featherweight Championship

Kickboxing record

Amateur record 2018-05-13 Win Yuta Takahashi 1st WMC Japan Amateur Tokyo, Japan Decision 2 2:00 2017-07-16 Win Hirokazu Urahashi Muay Thai Super Fight Suk Wan Kingthong vol.8 Tokyo, Japan Decision 2 2:00 2017-06-04 Win Tomoya Kawashima Bigbang Amateur 40 Tokyo, Japan Decision 2 1:30 2017-01-22 Win Yusei Murai 5th WINDY Super Fight Tokyo, Japan Decision (Majority) 3 2:00 2015-08-02 Loss Nadaka Yoshinari Suk Wan Kingthong Amateur, Tournament Final Tokyo, Japan TKO (Referee Stoppage) 2 0:39 2015-08-02 Win Eiji Katsura Suk Wan Kingthong Amateur, Tournament Semi Final Tokyo, Japan Decision (Unanimous) 2 1:30 2015-08-02 Win Kaede Hoshino Suk Wan Kingthong Amateur, Tournament Quarter Final Tokyo, Japan Decision (Majority) 2 1:30 2014-06-01 Win Shuto Date Bigbang Amateur 21 Tokyo, Japan Decision 2 1:30 2013-08-10 Win Asahi Shinagawa MAJKF KICK GUTS 2013 Tokyo, Japan Decision (Unanimous) 2 2:00 2013-06-02 Win Ryuki Yoshida Bigbang Amateur 14 Tokyo, Japan KO 2012-09-23 Loss Tensei Nakajo MAJKF Kick BREAK-29 -SHARPLY- Tokyo, Japan Decision (Unanimous) 3 1:30 Legend:

Mixed rules record Win

Dawsakorn Mor.Tassanai KO (left hook to the body) INOKI BOM-BA-YE x Ganryujima

Tokyo, Japan Ganryujima rules.