|Date of birth||5 March 1989|
|Place of birth||Fukuyama, Hiroshima, Japan|
|Height||1.77 m (5 ft 9 1⁄2 in)|
|2004–2006||Kyushu International University|
|2013–2014||→ Nagoya Grampus (loan)||42||(12)|
* Senior club appearances and goals counted for the domestic league only and correct as of 9 December 2013.
After he moved back from Brazil to Kitakyushu, Fukuoka, he played soccer at local elementary school and junior high school clubs, before he joined the Kyushu International University High School club, and played two matches at the 85th All Japan High School Soccer Tournament.
He joined Fukuoka University club in April 2007. 3 months later he played at the AJHSST, and won the 33rd Prime Minister's Cup All Japan College Soccer Tournament in 2009.
While playing for the Fukuoka University Club, Nagai also played for Avispa Fukuoka in the J. League Division 2 in 2009 and Vissel Kobe in 2010 as a designated player for development by the league and JFA.
He was transferred from Nagoya to Standard Liège of Belgian Pro League in January 2013, but transferred back to Nagoya on loan from August 2013 to June 2014, due to less playing opportunities given with Standard Liège. In January 2015, the loan deal was terminated as Nagai moved back to Nagoya on a permanent basis.
2Includes J. League Cup.
3Includes AFC Champions League.
4Includes Belgian Pro League Play-offs.
- As of 10 August 2012
- Nagoya Grampus
- AFC U-19 Championship Top scorers (1) : 2008
- Summer Universiade Top scorers (1) : 2009
- Asian Games Top scorers (1) : 2010
- 九州国際大付に韋駄天／高校サッカー (in Japanese). Nikkan Sports. 17 December 2006. Retrieved 28 July 2012.
- "Japan Coach Takeshi Okada Names Young Squad For Yemen Test". Goal. 23 December 2009. Retrieved 11 January 2009.
- "Japan rally past Yemen, qualify for 2011 Asian Cup". Japan Football Association. 7 January 2010. Retrieved 11 January 2009.
- "Japan - Kensuke Nagai - Profile with news, career statistics and history". Soccerway.com.
- "Ｕ－22日本代表 中東遠征 国際親善試合（vsクウェート代表）試合結果、監督・選手コメント". Japan Football Association (in Japanese). 10 February 2011. Retrieved 22 April 2011.
- "Ｕ－22日本代表 中東遠征 国際親善試合（vsU-22バーレーン代表）試合結果、監督・選手コメント". Japan Football Association (in Japanese). 13 February 2011. Retrieved 22 April 2011.
- "国際親善試合 U-22日本代表 vs. U-22ウズベキスタン代表 第1戦 試合結果". Japan Football Association (in Japanese). 26 March 2011. Retrieved 1 May 2011.
- "国際親善試合 U-22日本代表 vs. U-22ウズベキスタン代表 第2戦 試合結果". Japan Football Association (in Japanese). 29 March 2011. Retrieved 1 May 2011.
- "U-22日本代表 国際親善試合 2011_06_01 オーストラリア". Japan Football Association (in Japanese). 1 June 2011. Retrieved 1 June 2011.
- "U-22日本代表 国際親善試合 2011_08_10 エジプト". Japan Football Association (in Japanese). 10 August 2011. Retrieved 10 August 2011.
- "キリンチャレンジカップ2012 対U-23ニュージーランド代表". Japan Football Association (in Japanese). 12 July 2012. Retrieved 27 July 2012.
- 杉本選手のゴールでベラルーシを下す. Japan Football Association (in Japanese). 19 July 2012. Retrieved 27 July 2012.
- 大津の決勝ゴールでメキシコに競り勝つ. Japan Football Association (in Japanese). 22 July 2012. Retrieved 27 July 2012.