is a professional Japanese baseball player. He plays pitcher for the Saitama Seibu Lions. He previously played in NPB for the Yomiuri Giants and Hokkaido Nippon-Ham Fighters.
On October 25, 2012, Kumon was drafted by the Yomiuri Giants in the 2012 Nippon Professional Baseball draft.
On September 25, 2013, he made his debut as a relief pitcher in the Central League against the Tokyo Yakult Swallows.
In 2013 - 2016 season, Kumon pitched 15 games in the Central League.
On November 2, 2016, Kumon and Taishi Ohta was traded to the Hokkaido Nippon-Ham Fighters in exchange for Mitsuo Yoshikawa and Shingo Ishikawa.
In 2017 season, he finished the regular season with a 41 Games pitched, a 3âÂÂ0 WinâÂÂloss record, a 2.70 ERA, a 3 Holds, a 33 strikeouts in 36.2 innings.
In 2018 season, he finished the regular season with a 57 Games pitched, a 2âÂÂ0 WinâÂÂloss record, a 2.17 ERA, a 11 Holds, a 52 strikeouts in 54.0 innings.
On August 29, 2019, Kumon broke the NPB record for undefeated pitchers in 165 games. In 2019 season, he finished the regular season with a 61 Games pitched, a 2âÂÂ0 WinâÂÂloss record, a 3.96 ERA, a 17 Holds, a one Save, a 31 strikeouts in 52.1 innings.
In 2020 season, he finished the regular season with a 29 Games pitched, a 0âÂÂ2 WinâÂÂloss record, a 7.88 ERA, a 8 Holds, a one Save, a 19 strikeouts in 24.0 innings.
On August 12, 2021, Kumon and Shota Hiranuma was traded to the Saitama Seibu Lions in exchange for Fumikazu Kimura and Ryusei Satoh.