Kengo Ida set a national record in the men's 50-meter butterfly on Tuesday, the opening day of the Japan Swimming Championships.

Ida clocked 23.27 seconds to defend his title in the final over the non-Olympic distance at Tatsumi International Swimming Center. He trimmed 0.13 seconds off the previous national record he set at last year's tournament and finished 0.13 ahead of Takeshi Kawamoto.

In the men's 400-meter freestyle final, Keisuke Yoshida claimed his first championship by touching the wall in 3 minutes, 47.10 seconds. Kosuke Hagino, who holds the national record for the distance, is not competing at the tournament.

Sixteen-year-old Miyu Namba won the women's 400 freestyle with a time of 4:09.39.

Also missing from this year's national championships is teenage star Rikako Ikee, who was diagnosed with leukemia in February and forced to skip the meet — which serves as a qualifier for the world championships — in order to focus on treatment.

The Japan Swimming Federation is collecting messages of encouragement from swimmers and fans for the 18-year-old during the seven-day meet.

The federation has prepared 5,000 postcard-size sheets of paper for fans and competitors to write messages. Officials of the sport's governing body will hand out the sheets to competitors who advance to the finals of an event, while a stack will be placed near the entrance during the meet.

The messages will be delivered to Ikee after the meet finishes on Monday.

In addition to winning six gold medals at last summer's Asian Games in Jakarta, Ikee holds national records over 50, 100 and 200 meters in freestyle, as well as 50 and 100 in butterfly.