Yasuhiro Koseki is a Japanese breaststroke specialist and Asian Record Holder. Born March 14, 1992 Koseki was one of the frontrunners in the 200 breaststroke on the road to Rio, constantly posting some of the world’s fastest times, but at the games, he was unable to take home any medals. Koseki broke the Asian Record in the 200-meter short course breast back in 2014.
2014 Japan Short Course Championships
Going into the National Championships Koseki was known as a rising star, but he blew expectations out of the water in February 2014. Koseki started the meet off by breaking the Asian and Japanese Record in the 100-meter breast, going 56.34 (short course meters) for the win. The following day he stunned with his second record of the meet, this time putting up a 26.47 in the 50-meter breast, and finished his meet the following day with the 200-meter breast. Koseki went 3-for-3 and broke another national record in the 200-meter breast, a record previously held by Kosuke Kitajima.
2015 Japanese National Championships
In April of 2015 Koseki led a group of Japanese swimmers that proved they are among the world’s best in the 200-meter breast. Posting a 2:07.77, Koseki finished 1st about two seconds ahead of the field, but his competitors finished with the top four times in the world at the time.
2015 World Championships
At the 2015 World Championships in Kazan Koseki competed in the 200-meter just a few months after posting one of the world’s top times in the event. He posted the meet’s fastest time in the semi-finals, going 2:08.03, but in the championship final Koseki tightened up on the back-half. He struggled to finish the last 50 meters and was pushed out of medal contention, finishing 5th overall in 2:09.12.
2016 Rio Olympic Games
In his Olympic debut, Koseki made the final in each of his three events, but missed out on medal places. In the 200 meter breaststroke, like the World Championships, he went out fast. Koseki was leading the field at the 50, 100 and 150 meter mark but fell off dramatically in the final 50. A split of 34.06 saw him fall from 1st to 5th, where he finished in 2:07.80.
In the 100 meter breaststroke, Koseki finished 6th in 59.37 and in the 400 meter medley relay he helped Japan to a 5th place finish.
2017 World Championships
In the 100 meter breaststroke in Budapest Koseki again finished just off the podium. He touched in 59.10, just 0.05 away from the bronze medal.
But in the 200 meter breaststroke he made it on there. He won the silver medal in 2:07.29 behind Anton Chupkov of Russia.
2018 Pan Pacific Championships
On day 1, Koseki made a statement swim by capturing gold in the men’s 100 breaststroke, touching in a time of 59.08, just .04 off of Kosuke Kitajima’s meet record. He also had relay duties that night on the 400 mixed medley relay, splitting 58.57 to aid Japan finish 2nd for silver. On day 4, Koseki touched 4th in the 200 breast in a time of 2:08.25, just outside of the medals. He finished off his pan pacs performance that day with a silver in the men’s 4×100 medley relay, splitting 58.62 on breaststroke.
2018 Asian Games
Koseki continued his momentum from Pan Pacs and swam to a clean sweep in the men’s breaststroke events, winning the 50 (27.07), 100 (58.86, games record), and 200 (2:07.81). He also helped Japan to silver medals in the 4×100 medley and mixed medley relays, the former setting a new Japanese record (3:30.03).
2018 Short Course World Championships
In Hangzhou, Koseki swam to a bronze medal in the 100 breast (56.13), setting a new Asian record and falling only .12 outside of the gold medal winning time. He also helped Japan to a bronze medal in the 4×100 medley relay, splitting 55.91 to help break another Asian record.