is a Japanese male table tennis player. He is the gold medalist at the 2010 Youth Olympics and he won the World Junior Table Tennis Championships in 2010 (doubles) and 2011 (singles).

On 21 April 2012, he defeated Ma Long of China, World Rank no 1, which he became the first player qualified for 2012 Olympics from the Asian Olympic Qualifiers.

Since 2012, he has been playing for the German Team TTC matec Frickenhausen.

He also won the 2014 Russian Open singles title.

Career Junior career Niwa had a prolific junior career that began on 2008. He reached the quarter-finals at the 2008 India Junior Open in Pune, India, and won the doubles title with his partner, Yuki Hirano. At the 2008 World Junior Championships in Madrid, Spain, he partnered with Kenta Matsudaira to reach the semi-finals. On the following year, Niwa partnered with Asuka Machi to win the 2009 ITTF Cadet Challenge and ITTF Junior Circuit Finals in Tokyo, Japan.

At the 2009 World Junior Table Tennis Championships, Niwa reached the quarterfinals in the men's singles event before he was defeated by Lin Gaoyuan. Niwa qualified for the 2009 World Table Tennis Championships in Yokohama, Japan by defeating Josef Simoncik in the qualification tournament. Niwa reached 64 round before he lost over Germany's Dimitrij Ovtcharov.

At the 2010 Singapore Youth Olympics, he won a gold medal in the Boys' Singles Event, and a gold medal partnering Ayuka Tanioka in the Mixed Team event. Niwa won the U21 title at the 2011 Dortmund Pro Tour German Open by defeating Kim Min-seok. At the 2011 Incheon Pro Tour Korea Open, he defeated Jeoung Young-sik where he obtained his second U21 title that year. At the 2011 Manama World Junior Table Tennis Championships, he won the gold medal in the men's singles event, defeating Lin Gaoyuan of China.

2012: Breakthrough By 2012, the 17-year-old world junior champion was gaining widespread attention. His breakthrough came at the 2012 Asian Olympic Qualification Tournament where he overcame world ranked No. 1 Ma Long and became the inaugural Asian player in the sport to qualify for the Olympics.. olympic.org. Retrieved on 8 October 2017. Partnering with Kenta Matsudaira, Niwa overcame the Chinese pair of Wang Hao and Zhou Yu to win the 2012 World Tour Polish Open doubles title.

2013 Niwa qualified for the 2013 World Table Tennis Championships seeded 15. ittf.com. Retrieved 8 October 2017 He reached the fourth round in men's singles event before being defeated by Ma Long. He partnered Kenta Matsudaira in the doubles event and reached the third round before losing to compatriots, Jun Mizutani and Seiya Kishikawa. At the 2013 World Tour Japan Open in Yokohama, the "Niwa-Matsudaira" tandem lost in the finals against compatriots, Jin Ueda and Maharu Yoshimura.

2014: First ITTF World Tour Title At the 2014 World Team Table Tennis Championships in Tokyo, Niwa won 4 out of his 5 matches, contributing to Team Japan's bronze medal. At the 2014 World Tour Grand Finals in Bangkok, the Niwa/Matsudaira pair lost in the final to Korean pair Cho Eonrae and Seo Hyundeok. Niwa won the 2014 World Tour Russian Open title in the men's singles event, defeating England's Paul Drinkhall in the final. The Niwa/Matsudaira pair competed in the semi-finals and were defeated by the Russian pair Fedor Kuzmin and Grigory Vlasov.

2015 At the 2015 World Table Tennis Championships, Niwa reached the 4th round before being defeated by China's Fan Zhendong. In the doubles event, the Niwa/Matsudaira pair reached the semi-finals, and were defeated by Fan Zhendong and Zhou Yu. This was the last international partnership with Kenta Matsudaira.

2016 At the 2016 World Team Table Tennis Championships in Kuala Lumpur, Niwa contributed to Team Japan's success in winning the silver medal. The team lost to Team China in the final. Niwa represented Japan at the 2016 Summer Olympics in the men's singles event. He reached the quarterfinals before being defeated by eventual silver medalist Zhang Jike. In the Men's team event, Niwa contributed to team Japan's first silver medal in the category. However, Niwa expressed discontentment with his performance, not winning any singles matches. shueisha.co.jp. Retrieved 8 October 2017.

2017 Niwa began the year by winning a bronze medal at the 2017 ITTF Asian Championships in Wuxi, China. In the quarterfinals, he defeated world ranked #3 Xu Xin, but lost to Korea's Jeong Sangeun in the semi-finals. At the 2017 World Table Tennis Championships, Niwa partnered with Maharu Yoshimura to win the bronze medal. The Niwa/Yoshimura pair reached the semi-finals where they lost to Chinese pairing and eventual champions Fan Zhendong and Xu Xin in the men's singles event, he reached the quarter-finals, defeating Dimitrij Ovtcharov in the fourth round, and losing to Fan Zhendong in the quarterfinals. At the 2017 World Tour Japan Open, the Niwa/Yoshimura pair reached the finals of the men's doubles event where they lost to the Chinese pairing of Ma Long and Xu Xin.

2021 In March, Niwa played in the WTT Star Contender event at WTT Doha, but he had an early round of 32 exit to Gustavo Tsuboi.

Niwa played in the singles and team event of the 2020 Summer Olympics. Niwa beat Wang Yang in the round of 32 but lost to Dimitrij Ovtcharov in the round of 16 in the men's singles event at the Tokyo Olympics. In the team event, Japan beat Australia in the round of 16. In the quarterfinals, Niwa upset Mattias Falck to lead to Japan's victory over Sweden. In the semifinals, Japan lost to Germany but won the bronze medal after beating South Korea.

Retirement Niwa retired from international competition in November 2022 stating that he wanted to "pass the baton on to the next generation and support them" but will continue to actively compete within Japan.

Major League Table Tennis (MLTT) Following his retirement from international play, Niwa joined Major League Table Tennis (MLTT) in the United States for the 2024–2025 season. He was selected as the No. 2 overall pick in the draft by the New York Slice.

Doubles Partners Niwa / Matsudaira Niwa and Kenta Matsudaira were doubles partners from 2008 to 2015. Their playstyle is characterized by both players' unorthodox playstyles, with Niwa frequently incorporating "chiquita" banana flicks and Matsudaira frequently using his tomahawk service. Both players frequently use their backhand to win points.

The pair first competed in the international scene at the 2008 Cetniewo Polish Youth Open. In 2012, they defeated the Chinese pairing of Wang/Zhou to secure their first men's doubles titles in the ITTF world tour scene. The pair won a bronze medal at the 2015 World Table Tennis Championships. Niwa and Matsudaira have not partnered on the international scene since 2015.

Niwa / Yoshimura Niwa and Maharu Yoshimura have been frequent doubles partners starting in 2016. The pairing first rose to prominence at the 2016 Summer Olympics Men's Team Event where the pair contributed to Japan's silver medal. At the 2017 Asian Championships in Wuxi, the pair reached the semifinals before losing to Fan Zhendong/Lin Gaoyuan. At the 2017 World Table Tennis Championships Men's Doubles event, the pair won a joint bronze medal. The following month, at the 2017 World Tour Japan Open, Niwa/Yoshimura reached the finals before losing to Ma Long/Xu Xin in three straight games.

Niwa / Mizutani Koki Niwa and Jun Mizutani were expected to play doubles in the team event (alongside Tomokazu Harimoto as the ace player) at the Tokyo Olympics in 2021. Mizutani noted the uniqueness of having a doubles pair with two left-handed players and stated that their objective was to make the match as un-normal as possible.

Rivalries Niwa vs. Chen Chien-an Niwa and Chen have met 9 times in the international scene, with Niwa leading 5–4. Their first encounter was at the 2009 Harmony China Open where Niwa won 4 games to 1. They met another two times at the 2011 Harmony China Open where Chen defeated Niwa in the U21 Men's singles final, and Niwa defeated Chen in the Men's singles main bracket. In their most recent encounter, Chen won 4 games to 2 over Niwa at the 2017 Asian Cup main tournament bracket, and Niwa won 3 games to 0 in the group stage.

Niwa vs. Kim Min-seok Niwa and Kim have met 10 times with Niwa leading 6–4. Their first encounter was at the 2009 Korea Open U21 Men's singles event where Niwa won in full games. Niwa and Kim have met 3 times in the semi-final stages of U21 pro tour events. At the 2011 Pro Tour Germany Open U21 Men's singles final, Niwa won in full games over Kim. Their most recent encounter was in 2015 where Niwa won 4 games to 1 at the 2015 World Tour China Open.

Career statistics

ITTF Major tournament performance timeline +KeyWFSFQF#RRR (W) Won; (F) finalist; (SF) semifinalist; (QF) quarterfinalist; (#R) rounds 4, 3, 2, 1; (RR) round-robin stage; (S) Singles Tournament; (D) Doubles Tournament; (MD) Mixed Doubles Tournament; (T) Team Tournament. Tournament2009201020112012201320142015201620172018World CupSQFQFQFTSFSFFWorld ChampionshipsS2R2R4R4RQFTSFSFFQFD1R3R3RSFSFMD1R4RWorld Tour Grand FinalsS1R1RQF1R1R1R1RDQFFFOlympic GamesSQFTQFF

ITTF Career Singles Finals: 1 ResultDateTournamentTierOpponentScore WinNovember, 2014Airports of Regions Russian Open; RussiaWorld Tour Paul Drinkhall12-14, 11–8, 11–5, 11–7, 11–7

ITTF Career Doubles Finals: 10 ResultDateTournamentTierPartnerOpponentsScoreWinJuly, 2010Japan Open; JapanPro Tour Kenta Matsudaira Jiang Tianyi Leung Chu Yan6-11, 11–5, 7–11, 13–11, 11–4, 14–16, 11–1WinOctober, 2010JOOLA Hungarian Open; HungaryPro Tour Kenta Matsudaira Jun Mizutani Kaii Yoshida11-8, 11–8, 11–6, 8–11, 8–11, 11–8Runner-upJuly, 2011Japan Open; JapanPro Tour Kenta Matsudaira Lin Gaoyuan Wu Jiaji6-11, 9–11, 11–9, 7–11, 9–11WinNovember, 2012Polish Open; Poznan, PolandWorld Tour Kenta Matsudaira Zhou Yu Wang Hao8-11, 11–7, 11–7, 11–6, 12–10Runner-upJune, 2013Japan Open; JapanWorld Tour Super Series Kenta Matsudaira Jin Ueda Maharu Yoshimura11-7, 8–11, 6–11, 8–11Runner-upAugust, 2013Harmony Open; ChinaWorld Tour Kenta Matsudaira Ma Long Xu Xin11-7, 4–11, 7–11, 5–11Runner-upMarch, 2016Qatar Open; QatarWorld Tour Super Maharu Yoshimura Fan Zhendong Zhang Jike8-11, 9–11, 7–11Runner-upApril, 2016Polish Open; PolandWorld Tour Major Maharu Yoshimura Masataka Morizono Yuya Oshima14-16, 8–11, 8–11Runner-upJune, 2017LION Japan Open; JapanWorld Tour Platinum Maharu Yoshimura Ma Long Xu Xin9-11, 3–11, 7–11WinSeptember, 2017Austrian Open; AustriaWorld Tour Platinum Jin Ueda Filus Ruwen Walther Ricardo11-7, 9–11, 11–9, 11–8

ITTF Junior & U21 Singles Titles: 8 No.DateTournamentTierOpponentScore1.July 2008Tahiti Junior Open, French PolynesiaJunior Circuit Cadet Boys Asuka Machi11-9, 10–12, 7–11, 11–8, 11–72.July 2008Tahiti Junior Open, French PolynesiaJunior Circuit Junior Boys Yuki Hirano11-9, 11–5, 7–11, 9–11, 8–11, 11–3, 7–113.November 2008Cadet Challenge & Junior Circuit FinalsJunior Boys Omar Assar11-8, 11–9, 9–11, 11–9, 11–84.March 2010German OpenPro Tour U21 Hiromitsu Kasahara11-6, 11–9, 11–7, 11–55.October 2010JOOLA Hungarian Open, HungaryPro Tour U21 Liu Yanan11-4, 11–1, 7–11, 11–7, 11–96.February 2011German Open, GermanyPro Tour U21 Kim Min-seok9-11, 6–11, 11–8, 11–7, 10–12, 11–8, 11–67.June 2011KRA Korea Open, KoreaPro Tour U21 Jeoung Young-sik11-5, 11–7, 9–11,9-11,6-11,11-78.November 2011Volkswagen World Junior Table Tennis Championships, BahrainJunior Boys Lin Gaoyuan3-11, 11–6, 7–11, 11–8, 13–11, 11–9

ITTF Junior & U21 Doubles Titles: 5 No.DateTournamentTierPartnerOpponentsScore1.July 2008Tahiti Junior Open, French PolynesiaJunior Circuit Cadet Boys Asuka Machi Kong Lingnan Wu Kevin11-9, 11–5, 11–42.July 2008Tahiti Junior Open, French PolynesiaJunior Circuit Junior Boys Asuka Machi Yuki Hirano