72nd TOKAI HIGH SCHOOL ATHLETIC MEET
- Friday, July 18th – Sunday, July 20th
- Mie Kotsu G Sports Forest Suzuka Swimming Pool
- LCM (50m)
- Results
Competing at the 72nd Tokai High School Athletic Meet, 16-year-old Yumeki Kojima of Japan blasted a lifetime best of 4:09.38 to score a new World Junior Record in the 400m IM.
Kojima beat his domestic field by nearly 12 seconds en route to slicing over half a second off the former WJR of 4:10.02 Russian Ilya Borodin put on the books at the 2021 European Championships.
Entering this competition, Kojima already owned an impressive personal best of 4:11.67. That time was produced just last month while competing at the 79th Aichi Prefectural High School Swimming Competition.
Kojima’s previous career-swiftest performance entering that two-day competition sat at the 4:17.42 he notched at last year’s Japanese High School Championships. That means he has hacked nearly 8 seconds off his best-ever 400m IM this past year en route to becoming Japan’s 4th-best performer of all time at just 16 years of age.
Japanese Men’s Top 10 LCM 400 IM Performers All-Time
- Kosuke Hagino – 4:06.05, 2016
- Daiya Seto – 4:06.09, 2020
- Tomoyuki Matsushita – 4:08.61, 2025
- Yumeki Kojima – 4:09.38, 2025
- Asaki Nishikawa – 4:09.63, 2025
- Kosuke Makino – 4:09.79, 2025
- Tomoru Honda – 4:09.98, 2023
- Yuya Horihata – 4:10.52, 2012
- Takeharu Fujimori – 4:10.90, 2017
- Kaito Tabuchi – 4:11.15, 2024
Split Comparison:
| Kojima’s New WJR – 4:09.38 | Borodin’s Old WJR – 4:10.02 | Kojima’s Previous PB – 4:11.67 |
| 56.43 | 57.44 | 57.31 |
| 1:03.59 | 1:03.87 | 1:04.99 |
| 1:11.03 | 1:10.41 | 1:10.39 |
| 58.33 | 58.30 | 58.98 |
The teen checks in as Japan’s 2nd-best performer of 2025, a year which has already seen Olympic silver medalist Tomoyuki Matsushita, Asaki Nishikawa and Kosuke Makino make dents in the nation’s all-time rankings.
In terms of the Japanese High School National Record, that remains at the 4:08.94 Olympic champion Kosuke Hagino put on the books at the 2012 Olympic Games; however, Kojima is creeping up on that mark to put it in serious jeopardy.
For additional perspective, 16-year-old Kojima’s 4:09.38 performance would represent a new United States National Age Group Record, destroying the 4:14.73 Olympic medalist Carson Foster established in 2018. That overtook Olympic legend Michael Phelps‘ previous age group standard of 4:15.20 logged in 2001.
Kojima now ranks 5th in the world on the season.
2024-2025 LCM Men 400 IM
MARCHAND
4:04.73
View Top 26»2 Bobby
FINKEUSA 4:07.46 06/05 3 Carson
Foster USA 4:07.92 06/06 4 TOMOYUKI
MATSUSHITA JPN 4:08.32 08/03 5 Ilya
BorodinRUS 4:09.16 08/03
What’s going on with japanese teens?
On a side note, when Hagino broke that in 2012, it was a High School Record but not a WJR?
FINA didn’t begin recognizing world junior records until 2014. They had initial benchmarks, but those were the world junior championship records.
I need what they’re feeding these kids
I didn’t even notice this one until I just saw that Ohashi lowered his 200 breast WJR. 2:06 at 16 years is bonkers.
Japan on the rebound after a lackluster couple of years… Spot 3-6 on the all time list in one year is bonkers. That’s gotta be insanely rare for any nation, esp one with Japan’s history of churning out top performers and OG medalists in this event.
I’m sorry what? These young breaststrokers and IMers are making Japan look really promising for 2028. Wouldn’t be surprised to see them on the podium.
Japan has to be developing young 200 Breaststrokers and 400 IMers directly from a factory or something
He must have crazy good techniques, which is not surprising for Japanese swimmers.
Is he going to WJs?