Nao Hibino avoided a first-round exit from the Istanbul Cup, coming from one-set down to beat world number 509 Dayana Yastremska 2-6 6-4 6-3.
Yastremska dominated Hibino's serve in the first set, breaking the sixth seed - ranked 444 places above her - three times to surge ahead.
Hibino suffered another break at the start of the second set, but recovered to force a decider against the 15-year-old Ukrainian wildcard - making her WTA main draw debut.
That momentum carried Hibino through to the end, but she had to fight off two break points in order to book a place in the second round.
Hibino's compatriot Kurumi Nara was unable to join her in advancing, going down 6-3 6-3 to Danka Kovinic.
Fifth seed Kovinic produced five aces to dispatch of Nara in 75 minutes.