While in junior high school, Kunori played for the academy of professional club Kyoto Sanga. He played as a midfielder, but his opportunities were limited due to the form of Shimpei Fukuoka and Genki Egawa.[1] Having failed to establish himself in the Kyoto Sanga youth team, he moved to Higashiyama High School, where he was converted to a striker, and established himself in the team.[1][2]
On 5 April 2023, Kunori scored his first hat-trick for the club against Balestier Khalsa with Albirex Niigata (S) winning the game 6–1. On 3 August, he scored four goals against Geylang International in a 6–1 win in which he also get himself his second hat-trick of the season. Kunori helped the club to retained the league title and finishing as the third highest league goal scorer behind Maxime Lestienne and fellow countrymen, Ryoya Tanigushi with 21 goals in 23 league appearances. In the 2023 Singapore Cup fixtures on 24 September, he rescued his team from a 1–0 deficit to draw level at 1–1 against DPMM.
Kunori would go on to win the league title at the end of the season with Albirex Niigata.[6] During the Football Association of Singapore Awards Night, he won the 2023 Young Player of the Year award and also being named in the league 2023 Singapore Premier League 'Team of the Year'.[7]
A forward with good technique, skilful dribbler and pinpoint passing ability, Kunori is also highly regarded for his vision and situational awareness.[2] He has been compared to fellow Japanese footballer Daichi Kamada for his style of play.[8]
^ ab"京都ユースに昇格できなかった悔しさが原動力、東山のエース・久乗聖亜「もっと怖い選手に」" [Motivated by the frustration of not being promoted to Kyoto Youth, Higashiyama's ace Seia Kunori ``becoming a scarier player]. soccer-king.jp (in Japanese). 12 August 2018. Retrieved 19 February 2023.
^ ab"22年ぶり選手権出場 チーム導く攻撃の要 久乗聖亜（京都・東山3年）" [Participating in the championship for the first time in 22 years Seia Kunori, the key to leading the attack of the team (Kyoto Higashiyama 3rd year)]. koukouseishinbun.jp (in Japanese). 19 December 2018. Retrieved 19 February 2023.
^"関西大学（６年ぶり１７回目）" [Kansai University (17th for the first time in 6 years)]. jfa.jp (in Japanese). Retrieved 19 February 2023.
^"＜東山＞決して驕らない"注目の逸材"久乗聖亜、ついに選手権へ【選手権出場校紹介】" [<Higashiyama> Seia Kunori, the never-to-be-arrogant “remarkable talent” finally enters the championship [Introduction of schools participating in the championship]]. soccer-king.jp (in Japanese). 27 December 2018. Retrieved 19 February 2023.
