Kosuke Kitajima suffered a shock defeat, while Ai Shibata cruised to her first national title as the Olympic champions had mixed fortunes on the opening day of the national swimming championships Thursday.
Kitajima, who won a breaststroke double in Athens last summer, finished third in the men's 200 meters behind Genki Imamura and Daisuke Kimura, and failed to win a place for the discipline in the world championships to be held in Montreal in July.
Imamura, who trailed Kitajima by 0.07 second at the halfway mark, touched the wall at Yokohama International Swimming Pool in 2 minutes, 11.70 seconds. Kimura overtook Kitajima down the final stretch to finish runnerup in 2:13.02, 0.24 of a second ahead of Kitajima.
Freestyle swimmer Shibata, gold medalist in Athens in the women's 800 meters, ended the six-year reign of Sachiko Yamada in the 400 as she held off her Olympic teammate by more than 3 seconds to claim her first national crown in 4:07.93.
Yamada, who owns the national record of 4:07.23, finished second in 4:11.37.
"You can't be satisfied with just the Olympic gold and I swam as if I were a challenger," Shibata said. "I'm disappointed that I was unable to break the national record, but I got a confidence boost with my first victory swimming alongside Yamada-san."
Shibata met the qualifying standard set by the Japan Swimming Federation with her winning time and booked a place in the world championships.
In other races, Maiko Fujino won the women's 400-meter individual medley in 4:41.96, while Daisuke Hosokawa took the men's 100-meter freestyle in 50.47.
Megumi Taneda emerged victorious in the women's 200-meter breaststroke in 2:28.62.