He was capped 80 times and scored 2 goals for the Japanese national team between 1980 and 1995. He made his first international appearance on 22 December 1980 in a World Cup qualifier against Singapore in Hong Kong. He scored his first international goal on 20 September 1986 in an Asian Games match against Nepal in Daejeon, South Korea.
He was a member of the Japan team that won the 1992 AFC Asian Cup. He played all the Japan games except one for which he wasn't eligible due to suspension.
He was such a key player that national coach Hans Ooft named him a member of the Japan squad for the AFC's final qualifying stage for the 1994 FIFA World Cup in spite of his injury. However, he could not play any game in the competition that was centrally held in Doha, Qatar as his recovery wasn't as good as Ooft had wished it to be. Japan's hope to qualify for the finals was dashed by a stoppage time Iraqi equaliser in the last qualifying match. The Japanese fans now refer to this match as the Agony of Doha, and his absence was one of the main reasons why Japan's campaign ended up unsuccessful.
After finishing his playing career, Tsunami worked as a pundit on television and as a coach at Tokyo Verdy's youth setup. He acquired the S-Class Coaching License that was a prerequisite to manage a J. League club in 2004.
In 2005, he was appointed the manager of J. League Division 2 side Vegalta Sendai. Vegalta finished fourth and failed to gain the promotion. Tsunami was dismissed after one season. In 2006, he became an assistant coach to new manager Ruy Ramos at another J2 side Tokyo Verdy. Again the team failed to move up and he was sacked after one season. In 2007, he became the manager of newly relegated J2 side Cerezo Osaka but was dismissed in May after a bad start.
In 2008, he was appointed as the manager of Division 2 club Yokohama FC but was fired at the end of the 2008 season.