The opening day of Japan's national championships featured some familiar names on Thursday in Nagoya. Most notably, ​Kosuke Hagino ​and ​Daiya Seto ​squared off in the men's 400m IM.

Seto, the 2016 Olympic bronze medalist, took the win with a quick 4:10.44. Hagino, the 2016 Olympic gold medalist, touched only 0.01 of a second behind in 4:10.45. While these are not jaw-dropping times for these two (Seto's best time is a 4:08.47, and Hagino's best time is a 4:06.05), it is certainly a good launching point for the World Championships this summer in Budapest, Hungary.​

Takeharu Fujimori ​touched very closely behind Seto and Hagino with a solid 4:11.26.​
​
Other notable performances included:​
​
​Rikako Ikee dropped a swift 25.51 in the women's 50m butterfly, just 0.01 off of her own junior world record of 25.50 set in July 2016. That is also the second-fastest time in the world this year behind ​Sarah Sjöström's​ 24.96 from the Swim Open in Stockholm last week.​

​Katsumi Nakamura ​had a fantastic performance in the men's 100m freestyle, dropping a very quick 48.26 -- the third-fastest time in the world this year behind Aussies ​Cameron McEvoy​ (47.91) and ​Kyle Chalmers​ (48.20).​
​
The women's 100m breaststroke was a very quick, and close, race as well. The current world leader in 2017, ​Reona Aoki ​(1:05.29), took home the victory with a strong 1:06.77. She was followed closely by ​Satomi Suzuki ​in 1:06.91 and ​Kanako Watanabe​ in 1:07.09.​
​
The men's 100m breaststroke featured the current world-record holder in the 200m breaststroke, ​Ippei Watanabe​. However, Watanabe settled for second in 1:00.11 behind the champion ​Yasuhiro Koseki​, ​who touched in 59.26. It will be interesting to see what Watanabe will pull off in the 200m breast later on in the meet.