She ousted Hibino with 6-2, 6-2 after winning Sweden's Johanna Larsson earlier this week.
Ostapenko will now face Paraguay's Veronica Cepede Royg (WTA 77).
Jelena Ostapenko advances to #KoreaOpen Quarterfinals!
— WTA (@WTA) September 21, 2017
She ousts Hibino after 25 winners 6-2, 6-2! pic.twitter.com/hm1iCh0k8E
The French Open winner is the top seed in Seoul and is vying for the $250,000 prize pool.