Nagai's consistent performances in the J.League earned him a call-up to the Japanese national team in 1998. He made his international debut on February 15, 1998, against Australia, scoring a goal in a 3-0 win. Over the course of his international career, Nagai earned 84 caps, scoring 31 goals and becoming one of Japan's top goal-scorers.
"You don't have to say it."