17-Year-Old Yumeki Kojima Fires Off 1:56.53 200 IM World Junior Record

101st JAPAN SWIM

• Thursday, March 19th – Sunday, March 22nd
• Tokyo Aquatics Center
• LCM (50m)
• Meet Central
• SwimSwam Preview
• Day 1 Recap/Day 2 Recap
• Live Results

We already saw one World Junior Record fall on day three of the 2026 Japan Swim, with 17-year-old Shin Ohashi crushing a time of 2:06.59 in the men’s 200m breaststroke, but Yumeki Kojima also wanted to join the history-making party.

Racing in tonight’s 200m IM final, 17-year-old Kojima ripped a monster time of 1:56.53 to snag the silver behind Olympic medalist Tomoyuki Matsushita‘s gold medal-winning result of 1:55.71.

In doing so, Kojima overtook Hungarian Olympic champion Hubert Kos‘ longstanding WJR of 1:56.99 established at the 2021 European Championships.

Comparing the splits, Kojima was quicker on the backhalf, including a final 50m of 27.65.

Entering this competition, Kojima’s lifetime best in this event rested at the 1:57.32 he produced for silver at the 2025 World Junior Championships. That performance rendered him Japan’s 9th-fastest man in history. His new 1:56.53 WJR, however, bumps him up significantly on that list to now rank 5th as he hacked nearly a second off that prior outing.

Top 5 Japanese LCM 200 IM Performers All-Time

1. Kosuke Hagino – 1:55.07, 2016
2. Daiya Seto – 1:55.55, 2020
3. Tomoyuki Matsushita – 1:55.60, 2025
4. Kosuke Makino – 1:55.85, 2025
5. Yumeki Kojima – 1:56.53, 2026

Kojima already owns the 400m IM World Junior Record, courtesy of the 4:09.38 logged at a domestic meet last year.

The teen’s feat here checks him in as the #5 performer in the world at the moment. It also cleared the Japanese Swimming Federation (JASF) mandated selection standard of 1:57.23 needed to qualify for this year’s Pan Pacific Championships and Asian Games.