The driver was found dead by the driver of a Ford Transit van, who called the police after spotting the wreckage of the red Vauxhall Corsa.
Officers say they believe the tragedy happened sometime between 1am and 5.45am, the time the car was discovered.
The road was closed for specialist investigations for around eight hours on Sunday and traffic was diverted.
Anyone with information is asked to come forward.
Sergeant Stephen Quinn from Fife’s road policing unit said: “I wish to take this opportunity to extend Police Scotland’s sympathies to the family of the driver and our investigations to determine exactly what happened during this incident are ongoing.
“Anyone who was on the B922 during the early hours of Sunday May 5 and can provide us with any relevant information should contact police immediately.
“Likewise, if you believe your vehicle’s dash-cam footage may have captured this collision then please also get in touch.”
The road policing department can be contacted via 101 and witnesses should quote incident number 997 of May 5.