The 39-year-old Cavendish, the record stage winner on the Tour with 35, is set to compete in the final race of his storied career next week in Singapore.
But he said last week that he "will see" about racing in next year's Tour de France, explaining that he "saw things a bit differently" despite previously vowing not to compete in it again.
When asked if the Singapore race would definitely be his last, the British rider said: "I'm here in Saitama.
"I'm not here to talk about my future, I'm here to talk about the Saitama Criterium."
Cavendish finished third in driving rain in Japan after a furious finish that saw Eritrea's Girmay pip Slovenia's Primoz Roglic at the finish.
Roglic, who won the Vuelta a Espana for a record-equalling fourth time in September, broke away from the pack with around 3km to go.
Girmay, who became the first African to claim the Tour de France's green jersey for most sprint points in this year's race, reeled him in to win ahead of Roglic and Cavendish, with Belgium's Jasper Philipsen fourth.
"That's one of the nicest finishes for me," said Girmay.
"I just went all-out for the finish line."
Fans lined the street circuit despite constant rain in Saitama, north of Tokyo.
Girmay, who signed a contract extension with his Intermarche-Wanty team after his Tour de France success, was cheered on by a small group of Eritrean fans.
"If you win it's always special," said the 24-year-old.
"It doesn't matter if you win yesterday, if you win today that's always the best feeling."
Spain's Roger Adria did not finish after a crash with two other riders midway through the race.
Australia's Ben O'Connor withdrew beforehand after crashing in the time trial.
