Kazushi Imafuku Downs Kosuke Hagino’s 2013 JPN High School Record In 400 Free

101st JAPAN SWIM

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

Day one of the 101st Japan Swim already brought us two Japanese national records and a World Junior record, both on the men’s side.

We reported how 17-year-old phenom Shin Ohashi ripped a new lifetime best, JPN record and WJR in the men’s 100m breaststroke, posting 58.67 as tonight’s gold medalist.

Earlier, Shoon Mitsunaga produced a time of 23.06 to take the top seed out of the men’s 50m butterfly heats, tying the national standard Taikan Tanaka established last year.

An additional record bit the dust before the day was done, however, as 18-year-old Kazushi Imafuku crushed a new Japanese High School benchmark of 3:45.84 en route to winning the men’s 400m freestyle.

Imafuku wasn’t alone atop the podium, however, as World Championships bronze medalist Tatsuya Murasa, also 18 years of age, hit the same 3:45.84 result to share the gold.

Aiki Nishikawa rounded out the podium this evening, just a hair behind in 3:46.04 for bronze.

As for Imafuku, his performance represents a monster new lifetime best overtaking his previous PB of 3:47.77 nabbed at last year’s edition of this competition. That means Imafuku skipped 3:46 territory entirely to drop nearly two seconds off his prior quickest-ever effort.

Imafuku’s time was also nearly a second faster than the JPN High School record of 3:46.89, a time retired Japanese Olympic icon Kosuke Hagino put on the books over a decade ago in 2013.

Of note, both Murasa and Nishikawa also reaped new lifetime bests in tonight’s tight contest. Entering this competition, Murasa’s PB rested at 3:46.73 from the Japan Open last November, while Nishikawa had been as swift as 3:48.28 from the Intercollegiate Championships two months prior to that.

The trio shake up the all-time Japanese rankings in this 4free event, with Imafuku and Murasa now tied as the nation’s #3 performers ever and Nishikawa checking in as the 5th-speediest.

Top 5 Japanese Men’s LCM 400 Freestyle Performers All-Time

1. Kosuke Hagino – 3:43.90, 2014
2. Takeshi Matsuda – 3:4.99, 2008
3. Kazushi Imafuku, 3:45.84, 2026 & Tatsuya Murasa, 3:45.84, 2026
4. –
5. Asaki Nishikawa, 3:46.04, 2026

Splits for these stellar performances are below:

These men now rank just outside the list of top 5 performers in the world this season.