Ihara was rarely out of the spotlight in the emerging J1 League throughout the 1990s. He spent most of his career with Yokohama F. Marinos and formed a key defensive partnership with the flamboyant Tsuyoshi Kitazawa at club level. After graduating from University of Tsukuba, he joined Nissan Motors (later Yokohama Marinos) and rapidly rose through the Marinos youth ranks to become a key player. The long-serving Ihara was so important to his club that he was nicknamed Mister Marinos by many Japanese fans.[3] He formed the backbone of the club and also helped to bring on talented youngsters like Yoshikatsu Kawaguchi and Shunsuke Nakamura.
After leaving Marinos, Ihara also spent a season with Júbilo Iwata (2000) and his last 2 seasons with Urawa Reds (2001-2002). He retired in 2002. He played 341 games and scored 7 goals in the league. He was selected Best Eleven for 6 years in a row (1991/92-1997)
He then became the assistant coach for club Kashiwa Reysol in 2009, being the caretaker on two occasions.
After a horrible three years of being at the bottom half of the table in the J2 League, Avispa Fukuoka then hired Ihara as their coach, replacing the former Marijan Pušnik. Under Ihara, then club went on to win 24 games out of 42 and collected a total of 82 points, ending their regular season in third place. Avispa then went on to the playoffs, where they beat V-Varen Nagasaki 1-0, and then drew 1-1 against Cerezo Osaka. Avispa eventually ended up getting promoted to the J1 League as they were the higher-seeded team.
Ihara's first match in charge of Avispa in the 2016 J1 League was a 2-1 away loss against Sagan Tosu. The first win in the league was on their eighth match in a 0-1 away win in Tokyo against FC Tokyo.
