Gentildonna, winner of the Japanese 1000 Guineas, followed up in the Oaks at Tokyo racecourse.
The Japanese version of the Oaks, the Yushun Himba, was established in 1938 and acquired its current status as the Japanese Oaks when moving to Tokyo Racecourse in 1946.
The Yushun Himba opened its door to foreign-bred runners in 2003 and acquired international Group One status in 2010 although there were no international runners this year.
The race did feature the Guineas winner, however, and Sei Ishizaka's daughter of Deep Impact trounced her rivals by five lengths to take the second leg of the fillies' Triple Crown, breaking the race record by 1.7 seconds in the process.
Verxina, another Deep Impact filly, had to settle for second as she had in the Oka Sho (Guineas), finishing three parts of a length in front of Ice Follies who finished well to relegate I'm Yours to fourth.
Yuga Kawada, in the saddle for the first time with Yasunari Iwata suspended, held Gentildonna up in rear down the back straight.
They were still nearer last than first turning into the straight but Gentildonna came home powerfully to claim her second top-level success.
She became the 13th horse to capture two classic titles and will now aim to become the fourth filly to complete the Triple Crown in the Shuka Sho in October.