17-Yr-Old Kazushi Imafuku Clocks 3:47.77 400 Free Personal Best At Japanese World Trials

2025 JAPAN SWIM

• Thursday, March 20th – Sunday, March 23rd
• Tokyo Aquatics Centre
• LCM (50m)
• SwimSwam Preview #1
• SwimSwam Preview #2
• Meet Central
• Live Results

The 2025 Japan Swim saw day one unfold from the Tokyo Aquatics Centre, site of swimming action at the 2020 Olympic Games.

This competition represents the sole qualifying opportunity for Japanese swimmers for this summer’s World Championships.

As a deviation from past stiff selection criteria, this time around the Japanese Swimming Federation (JASF) has set the qualification standards at the World Aquatics ‘A’ cuts.

We reported how two swimmers broke already through with new records to kick off their campaigns at this elite meet.

First, 23-year-old Taikan Tanaka fired off a new national record of 23.06 en route to winning the men’s 50m butterfly. Runner-up Katsuhiro Matsumoto hit a mark of 23.32 to join Tanaka in dipping under the World Aquatics ‘A’ standard of 23.36.

• Taikan Tanaka Rips 23.06 50 Fly Japanese National Record

Then the women’s 200m IM saw 18-year-old Olympic finalist Mio Narita produce a lifetime best of 2:09.68 to establish a new Japanese National High School record.

Narita’s performance sliced .30 off 3-time Olympian Rikako Ikee‘s previous high school record of 2:09.98 put on the books in 2017. Ikee hasn’t competed in this event since returning to competition after her battle with leukemia in 2019.

Narita, along with tonight’s silver medalist Shiho Matsumoto (2:10.61), easily cleared the ‘A’ standard of 2:12.83 needed for Singapore.

• Mio Narita Cranks Out New Japanese National High School Record in 200 IM

The men’s and women’s 400m free events saw multiple swimmers clock Singapore-worthy times to keep the momentum rolling.

In the men’s race, 17-year-old Kazushi Imafuku got the wall first, clocking a time of 3:47.77 for the gold.

Imafuku’s outing represented a big-time personal best, easily overtaking the teen’s previous career-quickest result of 3:50.86 notched at last November’s Japan Open.

He now becomes Japan’s 10th-best performer of all time and ranks 6th in the world this season. Additionally, he dipped under the World Aquatics ‘A’ cut of 3:47.77 required for the World Championships. He was the only competitor to accomplish that feat.

For perspective, his new PB would render him the 7th-quickest American 17-18-year-old boy in history.

Imafuku has been a rising star in Japanese mid-distance freestyle. He has been tearing up the national rankings, highlighted by several SCM performances last year. He is also an accomplished open water athlete. You can read more about his performances here.

According to Hochi News, Imafuku conveyed after his victory, “I didn’t think I could win. I’ve been working hard and shifting my practice to the 800m and 1500m (freestyle), so I thought I was just swimming my best in the 400m… I was surprised.

“When I’m in the ocean (OWS), it’s 100% ocean, and when I’m competitive swimming, it’s 100% competitive swimming. In a year, I probably do competitive swimming about 60 or 70% of the time, and the rest is open water swimming.

“Now that I’ve won, I want to give it my all.”

Ichika Kajimoto topped the women’s 400m free podium, turning in a time of 4:07.58 for the gold. That held nearly a second advantage over Miyu Namba who clinched the runner-up spot in 4:08.55 as the only other sub-4:10 swimmer.

The World Aquatics ‘A’ standard rests at 4:10.23, so both women added their names to the Japanese roster in this event. Both women also slide onto the list of the season’s top performers, ranking 2nd and 3rd, respectively.

For additional perspective, Kajimoto now checks in as Japan’s 6th-quickest performer ever while Namba’s lifetime best of 4:05.25 from 2022 keeps her ranked #2 in history.

The men’s 100m breaststroke saw the top 5 finishers clear the 1:00 threshold, led by 24-year-old Yamato Fukasawa.

Fukasawa, who balances swimming with working at Tokyu Railways, topped the podium in a mark of 59.24, a new personal best by .17.

That gave him the edge over Taku Taniguchi who settled for silver a hair back in 59.30 while Yu Hanaguruma bagged the bronze in 59.70.

Hayato Watanabe and Ippei Watanabe claimed the 4th and 5th places with respective efforts of 59.85 and 59.87.

Both Fukasawa and Taniguchi were able to beat the ‘A’ standard of 59.75 to add their names to the Japanese lineup for Singapore.

University of Tennessee commit and Olympic finalist Mizuki Hirai roared to the wall in a time of 57.04 to deliver the victory in the women’s 100m fly.

Splitting 26.53/30.51, Hirai earned the gold ahead of 3-time Olympian and national record holder Rikako Ikee.

24-year-old Ikee, too, dipped under the World Aquatics ‘A’ cut of 58.33 with her silver medal-worthy time of 57.53. Hiroko Makino also landed on the podium in 58.22 for bronze.

Hirai has already been as quick as 56.99 this season to rank 2nd in the world behind American Regan Smith. Hirai’s previous outing was registered at January’s Kosuke Kitajima Cup.

Ikee’s result represents a new season-best to rank her 3rd in the world on the season.

After the race, Hirai told Nikkan Sports, “At the World Aquatics Championships, I will compete against the top athletes in the final, and do my best to win a medal and set a new Asian record (55.62 seconds).”

As for Ikee, she commented,  “I don’t want to end with a disappointing result like the Olympics (where she was eliminated in the semi-finals). If I run my own race, I believe the results will come naturally.” (Nikkan Sports)

Although Miki Takahashi struck gold in the women’s 100m back, her time of 1:00.71 was outside the ‘A’ standard of 1:00.46.

On the men’s side, Riku Matsuyama was also over the 53.94 ‘A’ standard, hitting 53.99 as the gold medalist.

Japanese World Championships Qualifiers Through Day One

• Taikan Tanaka – men’s 50m fly
• Katsuhiro Matsumoto – men’s 50m fly
• Mio Narita – women’s 200m IM
• Shiho Matsumoto – women’s 200m IM
• Kazushi Imafuku – men’s 400m free
• Ichika Kajimoto – women’s 400m free
• Miyu Namba – women’s 400m free
• Yamato Fukasawa – men’s 100m breast
• Yu Hanaguruma – men’s 100m breast
• Mizuki Hirai – women’s 100m fly
• Rikako Ikee – women’s 100m fly