The US Open champion took 71 minutes to overcome world No. 37 Giorgi in their first ever encounter, clearing the way for a trophy on home soil, reports Efe news.
"It was important for me to play two sets and not go three sets - also for recovery for the next tournament - and I needed a match like this", Pliskova, fourth seed, said after the win.
Elsewhere, Kiki Bertens fought back from a break down in the deciding set to beat Ajla Tomljanovic and claim her third title of the year at the Korea Open in Seoul. "I knew I had to play aggressive and make her move around the court, to play with all the energy I had in me and to be positive all the time - that was the goal". "As I am feeling very exhausted today, maybe I wasn't doing the little things well". "But the future is bright for her and congrats to her for an incredible few weeks". Kiki Bertens, now in eighth place, competes in the final of the Korea Open later on Sunday.
The Czech former world number one came into the contest having spent 419 minutes on court this week, more than any other player despite a first round bye and nearly twice as long as Osaka.
She can still, however, take heart from her recent run of form as she looks to finish the year on a strong note.
World No. 1 Simona Halep and Angelique Kerber are the only two who have secured their spots.
Osaka has been in the spotlight both on and off the court since arriving back in Japan after her historic win in NY.
But Osaka was still proud she had made the Tokyo final and added: "To play the final of the US Open and then to come here, I think I did pretty well".
10 Elise Mertens (Bel) 3,080 * Qualified.
Her first services had a success rate of over 80 percent. The world No. 8 was soon a set up after unleashing another brutal drive catching No. 7 Osaka flat-footed.
The newly-crowned US Open champion, who was bidding to become the first Japanese victor of the event since 1995, succumbed 6-4 6-4 in a battle of two big servers.
Things barely improved in the second set.
Osaka has carried the poise and power that saw her overcome Serena Williams in the Flushing Meadows final across the Pacific with her and, helped by eight double-faults from Giorgi, wrapped up the victory in just 72 minutes.