On January 27, 1988, when Ihara was a University of Tsukuba student, he debuted for Japan national team against United Arab Emirates. After debut, he became a regular player and he played at 1990 World Cup qualification and 1990 Asian Games. In 1992, Japan won Asian Cup first time. However, at 1994 World Cup qualification, Japan failed to won for qualify to 1994 World Cup. After that, Ihara became a captain for Japan and played at 1995 King Fahd Cup and 1996 Asian Cup. In 1997, at 1998 World Cup qualification, Japan won for qualify 1998 World Cup first time. During the 1998 World Cup in France, the veteran sweeper's experience was crucial to Japan's survival in their very first World Cup appearance, forming a flat back three defence with strong centre-back Yutaka Akita as well as speedy fullbacks Eisuke Nakanishi (or strong centre-back Norio Omura). Young Marinos goalkeeper, Yoshikatsu Kawaguchi was Japan's first choice goalkeeper at the time. After 1998 World Cup, he played at 1999 Copa América. This competition was his last game for Japan. He played 122 games and scored 5 goals for Japan until 1999.