Sakata made his Grand Prix debut in 1991 and steadily built his competence in the fiercely contested 125 cc class throughout the early 1990s. By the 1993 season he was challenging at the front of the championship, ultimately finishing second in the standings behind German rider Dirk Raudies while riding a Honda.
The 1994 season marked a significant milestone in Sakata's career and in Japanese motorsport history. He signed with the Aprilia factory, becoming the first Japanese rider to race for a European factory team in the 125 cc class. The move proved immediately successful. Sakata repaid Aprilia's confidence by winning the 125 cc World Championship that year, delivering the Italian manufacturer a prestigious title.
After his first championship, Sakata continued competing in the 125 cc class through the mid-1990s. He remained a front-runner across successive seasons, consistently challenging for podiums and race victories even as the class remained one of Grand Prix racing's most competitive.
Sakata claimed his second world championship in 1998 after a tight points battle that ran down to the final stages of the season. He held off challenges from Tomomi Manako and a young Marco Melandri — later to become a multiple world champion in his own right — to secure his second 125 cc title. The victory confirmed Sakata's status as one of the most durable champions in the lightweight class.
Sakata competed in the 1999 Grand Prix season before retiring from international competition. His career spanned nine years and two world championships, a record that placed him among the most accomplished Japanese riders of his generation.
Following his retirement from Grand Prix racing, Sakata channelled his experience into coaching and talent development. He became a motorcycle coach and trainer, working with the next generation of Japanese racers, and serves as principal of the MFJ Road Race Academy. In 2018, at the behest of his students, Sakata returned to competitive riding by participating in the All Japan Road Race Championship at Tsukuba Circuit in the J-GP3 class — his first return to the All Japan Championship in thirteen years.
Kazuto Sakata's two 125 cc world championships place him in an elite group of Japanese riders who have left a lasting mark on Grand Prix motorcycle racing. His role as the first Japanese rider to compete for a European factory in the 125 cc class opened a path that subsequent generations of Japanese racers would follow. His transition into coaching and his ongoing involvement in Japanese grassroots motorcycle racing have extended his contribution to the sport well beyond his competitive years.