FC Tokyo won the champions in 2004 J.League Cup first major title in the club history.

He became a regular player as right side back as Akira Kaji successor soon and played many matches every season for a long time.

In November 2003, Tokunaga was selected Japan U-20 national team for 2003 World Youth Championship.

On October 8, 2009, Tokunaga debuted for Japan national team against Hong Kong at 2011 Asian Cup qualification under manager Takeshi Okada.

In July 2012, Tokunaga was selected Japan U-23 national team as over aged for 2012 Summer Olympics.

[6] In July 2013, Tokunaga was selected Japan under manager Alberto Zaccheroni for 2013 East Asian Cup for the first time in 3 years.