New World Junior Record for Short Course 100m Breaststroke: 17-Year-Old Yusei Imaizumi Surpasses Shin Ohashi's Mark

On September 4, 2026, at the Niigata Prefecture High School Autumn Prefectural Tournament in short course meters, 17-year-old Yusei Imaizumi set a new World Junior Record of 56.35 seconds in the men's 100m breaststroke, slicing 0.30 seconds off Shin Ohashi's previous mark of 56.65. The next competitor finished over 7 seconds behind, highlighting his dominance. Imaizumi employed an aggressive front-half strategy, leading from the start and holding within 0.06 seconds of Ohashi's back half, showcasing improved turn efficiency and underwater dolphin kick. This improvement from his prior 57.18 seconds in six months signals rapid development in a growth phase. Japan is building a golden generation in breaststroke, with Imaizumi's Junior Pan Pacific golds adding international credibility. However, the low-tier event and SCM-to-LCM transfer questions temper its championship value. The rivalry with Ohashi creates intense domestic competition. Imaizumi's career is in the rising phase, with risks in pacing and expectations managed through consistent training at the Japan Swim trials ahead of LA 2028. The performance underscores Japan's deep talent supply chain and youth development system, positioning them as challengers to the USA in men's breaststroke.