World champion and Rostelecom Cup victor Evgenia Medvedeva once more dominated the women's short program, but the rising star of the show was young talent Polina Tsurskaya.
Kostner's performance to "Ne Me Quitte Pas" featured a triple toe-triple toe combination, a triple loop and a double axel.
Carolina Kostner of Italy was next with 74.57 points, followed by Polina Tsurskaya of Russian Federation with 70.04.
The ice dance competition will be headlined by three-time and reigning world champions Tessa Virtue and Scott Moir, who won their seventh Skate Canada title last month with a record score and will be the clear favorites in Osaka.
The Japanese nationals are December 19-24, after the Grand Prix Final in Nagoya, Japan. You have days when it is not so easy and you need to get into that fighting mode.
Olympic champion and home favourite Hanyu was forced to withdraw due to an ankle injury sustained during practice in Osaka. "I was able to take the first step".
World champions Wenjing Sui and Cong Han of China won the gold medal in pairs with 234.53.
Skating to "Hallelujah", the Chinese duo scored 79.43 points to finish ahead Ksenia Stolbova and Fedor Klimov.
And 30-year-old Voronov took the opportunity with both hands, recording a season's best 90.06 in the men's short programme to lead the competition.
At the practice on Thursday, he appeared to be favouring his right ankle but did not leave practice.
"I am very sorry to have everyone anxious about me", Hanyu said in a statement released by the Japan Skating Federation. He skated during the run through for his free skate, although he did not do any further jumps.
Voronov added a first place in Saturday's free skate to his win in Friday's short program to cruise to victory with 271.12 points.
Adam Rippon of the United States was second with 261.99, followed by Alexei Bychenko of Israel with 252.07.
The ISU Grand Prix of Figure Skating series consists of six events and culminates in the Grand Prix Final in Nagoya, Japan, next month. The men's, women's and pairs free skate is on Saturday.