Ihara was born in Koka on September 18, 1967. After graduating from University of Tsukuba, he joined Japan Soccer League club Nissan Motors (later Yokohama Marinos, Yokohama F. Marinos) in 1990. The club won the 2nd place in 1990/91 and 1991/92 season. He was also selected Best Eleven in 1991/92. In 1992, Japan Soccer League was folded and the club joined new league J1 League. The club won the champions in 1995 season. He was selected Best Eleven for 5 years in a row (1993-1997). He played 267 matches for the club until 1999. Toward the end of his career, he played for Júbilo Iwata (2000) and Urawa Reds (2001-2002).
On January 27, 1988, when Ihara was a University of Tsukuba student, he debuted for the 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.
In 2006, Ihara became an assistant coach for the Japan U-23 national team and spent two years. In 2009, he became an assistant coach for club Kashiwa Reysol and coached until end of 2014 season. He also managed the club as caretaker in July 2009. In 2015, he signed with J2 League club Avispa Fukuoka and became a manager. In 2015, Avispa won the 3rd place and was promoted to J1 League. However the club was relegated to J2 in a year. He resigned end of 2018 season.
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