Rie Kaneto improved her Japan record in the women's 200-meter breaststroke on Saturday.
Racing at the Aquatic Super Series competition in Perth, Australia, between Japan, Australia and China, Kaneto won her final in 2 minutes, 20.04 seconds.
The 27-year-old Kaneto set the previous record of 2:20.72 in 2009 while wearing a now-outlawed high-tech swimsuit and Satomi Suzuki matched it in the 2012 London Olympics.
"I had been thinking about going for a personal best, and I swam to an even better time," said Kaneto, who represented Japan at the 2008 Beijing Olympics but missed out on London.
"It would be good if this time lights a fire under my rivals. I want to work on refining my swimming as I go into the national championships."
Denmark's Rikke Pedersen holds the world record of 2:19.11.