As a boxer, he was known for his unpredictable style, sometimes marking completely unexpected victories, and often losing in extravagant fashion as well.
Born Yuji Suzuki in Awano, Tochigi Prefecture (now incorporated into Kanuma) in 1949, he originally intended to be a physical education teacher, but his family’s financial circumstances prevented him from pursuing higher education, leading him to move to Tokyo, where he began training in boxing while working several odd jobs.
He was known primarily as a rough, undisciplined fighter early in his career, but his technique improved greatly under the tutelage of American trainer Eddie Townsend.
He challenged Shinichi Kadota (who had knocked out Guts only five months earlier) in 1972, and won by decision to capture the OPBF Lightweight title.
Guts was re-introduced to González 32 years later on a Japanese television show, where he learned that he and Gonzalez bore an uncanny number of similarities, including being born in a poor household, and succeeding as an actor after retiring from boxing as former world champions.
The fight took place in Puerto Rico, and the country paid $200,000 (a rather large investment in the time period for a lightweight title match) to have Guts fight in Puerto Rico, showing Guts' widespread popularity at the time.
"OK Boku-jo" became the word of the year in Japan (2004), and Ishimatsu released a single CD, as well as a book describing his experiences inside and outside the ring, which became a best-seller.
"OK Boku-jo" and its other variations (such as "OK No-jo", which is meant to give a negative connotation) have become immensely popular (but still completely meaningless) in Japan.
He is credited with coining the word "Guts Pose" (ガッツポーズ, gattsu pōzu), now commonly used in the Japanese language.
Notables include Steven Spielberg's Empire of the Sun (1987) and Ridley Scott's Black Rain (1989).