The first match of the women's golf major tournament in Japan began in Ibaraki prefecture without spectators, and Ritsuko Ryu, 33 years old, who won 5 tours, took the lead alone with 6 unders.
Kasa went around with 7 birdies and 1 bogey under 6 under.
Momoko Osato, who finished second in the previous week's tournament, continued with a one-stroke difference of 5 under.
In addition, Erika Kikuchi and Mao Saigo are in 3rd place with a one-stroke difference, and Ai Suzuki and Mamiko Higa are in 5th place with 3 unders.
Mone Inami, who has won four wins on this tour, is 1 under and starts in 15th place with Momoko Ueda, who won the championship last week.
Erika Hara, who is aiming for three consecutive victories in the major tournament, was behind in 103rd place with 4 overs.