Nagayama's major stage debut was from 2003 to the beginning of 2005 for the role of the acrobatic Eiji Kikumaru in the Prince of Tennis musical series, Tenimyu, as part of the first generation Seigaku cast.
Less than two weeks before the second show, Remarkable 1st Match Fudomine, Kotaro Yanagi - who was playing the lead role of Ryoma Echizen at the time - was hospitalized after being accidentally hit by a car.
Because the musical's rehearsals were well underway and performance dates already set, several changes were made in the cast for the show: Nagayama was shifted over to Fuji due to J-pop singer Kimeru, who was playing the role of Fuji, having to step up as Echizen, and Ichitaro was brought back as Kikumaru.
Since Nagayama's graduation, the role of Kikumaru has been played by Osamu Adachi, Koji Seto, Kyousuke Hamao, Shouta Takasaki, and Yuta Koseki.
Nagayama, along with Kimeru and Endo, went to see Yanagi graduate from Tenimyu at the final performance of Dream Live 3rd in 2006.
Above all, Nagayama is earnest and serious about his work and his fans, and this has helped him build and maintain a loyal base of support worldwide.