Sosaku Koizumi

Position: Coach / Manager
Born: September 1993
Hometown: Yamaguchi Prefecture, Japan

He began sailing in 3rd grade at the Hikari Sailing Club Junior Team, and during junior high school, he represented Japan in international competitions. While attending Hikari High School, he overcame intense pressure to win the National Sports Festival (Kokutai), held in his hometown of Yamaguchi. At Waseda University, he led his team as captain, winning the Intercollegiate Individual Championships and contributing to consecutive team championships.

Even after graduating from university, he remained at the forefront of competitive sailing. Though he narrowly missed selection for the Tokyo 2020 Olympic team, he played a vital role in supporting the Japanese national team as a training partner to both the men’s team (Okada-Hokazono) and the women’s team (Yoshida-Yoshioka), who were selected as Olympic representatives.

While he achieved numerous top finishes at the All-Japan 470 Championships and National Sports Festivals (Kokutai), his greatest accomplishments include helping the Yamaguchi Prefectural team, which he belonged to for many years, earn multiple overall victories (the Emperor’s Cup) at the National Sports Festival. As staff for his alma mater, Waseda University Sailing Team, he also contributed to an incredible five consecutive overall victories, with seven Intercollegiate Championship wins in total.
His presence is invaluable in both the mental and managerial aspects of team support.

From his student days through the Tokyo 2020 campaign, he had a long-standing rivalry with Isozaki, pushing each other to higher levels. Deeply impressed by his skill, discipline, and dedication as a sailing partner, Isozaki personally asked him to take on the role of coach for the Paris 2024 Olympic campaign.

As a coach who stands close to the athletes, he supports the team in every way—mentally, physically, and technically—and enjoys great trust from the sailors. Once a fierce competitor to Isozaki, he now stands alongside him and his young partner Ito, serving as a spiritual pillar of the team as they pursue Olympic gold together.

(Photo: Kazushige Nakajima / Text: T.N.)