A patient race plan undoes Seto's seven-year mark
The 21-year-old led wire-to-wire inside SAGA Arena, touching the wall more than five seconds clear of the field. His time carved 0.48 seconds from the 3:54.81 standard Daiya Seto had held since the 2019 International Swimming League season.
Matsushita split the butterfly leg in 53.22 and turned from backstroke in 1:53.61.
A six-second leap from a quiet personal best
The performance demolished the 4:00.44 lifetime best Matsushita had set at the same competition two years earlier. Asaki Nishikawa took distant silver in 3:59.94, with 17-year-old Raito Numata third in 4:00.07.
Matsushita told reporters afterwards he had deliberately targeted the back half. "Honestly it was an extremely high-level record, and while I thought I could achieve it, the question was how — so I decided to focus on the back half," he said. "Seto-san himself is competing at this meet and is probably watching, so I'm glad I could do it right in front of him."
The record deepens a résumé already built at the highest level. Matsushita won 400m IM silver at the Paris 2024 Olympic Games and repeated as runner-up at the 2025 World Championships in Singapore, sitting fourth on the all-time long-course list with a 4:05.83 best.
He had spoken before the race of a lesson learned earlier in the season, when a misjudged pace cost him victory and prompted his coach to warn he had "not yet given 100%."
