Taio Kanai won the 110-meter hurdles championship, setting one of two Japan records on Sunday, the final day of the national athletics championships at Isshin Mirai Stadium.
Kanai broke Satoru Tanigawa's 14-year-old national record by 0.03 second to win his first national championship at the meet in Yamaguchi Prefecture.
The 22-year-old Kanai looked surprised when he saw his time, and only managed a slight fist pump.
"I'm completely blown away that I set this record. I still can't get my head around it," said Kanai, who hadn't run for the previous two days, preferring instead to focus on image training.
"It was the first time I've prepared that way. And when I awoke this morning, I felt I had done it just right."
Masateru Yugami captured his first national title in the men's discuss with a 62.16-meter throw, beating the previous national record by 1.42 meters.
The competition serves as a qualifier for Japan's team to this summer's Asian Games in Jakarta.
Yoshihide Kiryu, who holds Japan's 100-meter record, finished fourth in the 200, 0.35 behind Shota Iizuka, who won his third national title in 20.34.
"It was the first time I've run the 200 at the nationals," Kiryu said. "I felt like I was able to keep running right until the end. My form always breaks down over the last 100 meters, but I learned this time that I can maintain my own tempo."