Fifty-four minutes was all it took for Barty to wrap up a 6-2, 6-3 victory and set up a quarterfinal against No.6 seed Evgeniya Rodina.
Despite only turning 20 earlier this year, Barty is embarking on her second ascent of the tennis ladder. After a glittering junior career, she enjoyed instant success in the senior ranks, reaching three major doubles finals alongside fellow Australian Casey Dellacqua.
However, the stresses of life on tour soon took its toll on her teenage mind and body, prompting a 17-month hiatus. She has played sparingly since returning - a bone stress injury disrupted the momentum from an encouraging grass court campaign - but looked in fine form against Namigata, two breaks in the opening three games setting her on course for a comfortable victory.
Rodina overcame a slow start against Dalila Jakupovic, eventually triumphing, 2-6, 6-4, 6-1. Also advancing to the last eight in Taiwan were Olga Govortsova and Vitalia Diatchenko. Govortsova saved two match points to defeat Julia Boserup, 5-7, 7-6(5), 7-5, while 2014 champion Diatchenko saw off Miyu Kato, 7-5, 6-4.