Silk Sari was an emphatic winner of the DFS Park Hill Stakes at Doncaster for Newmarket-based Italian pair Luca Cumani and Andrea Atzeni.
Joint-owned and bred by Fittocks Stud, managed by the trainer's wife, Sara, she went off at 8-1 for what is known as the fillies' St Leger and quickened five lengths clear of Groovejet with stunning ease.
"I must say I'm surprised," said Luca Cumani.
"I thought she would run well - she's been in excellent form - but winning like that was unexpected.
"There's a mile and five Group race (Prix de Royallieu) on Arc weekend for fillies, she might go for that.
"After that she's going to Dubawi [for breeding], the bloodlines will suit, as well as attitudes and racing style."
Kiyoshi proved her considerable talents remain very much intact with a brilliant victory under the soon-to-retire Jamie Spencer in the Japan Racing Association Sceptre Stakes.
The Charlie Hills-trained three-year-old looked a potential world-beater following a jaw-dropping display in last year's Albany Stakes at Royal Ascot and subsequent placed efforts in the Moyglare and Cheveley Park Stakes meant connections headed into the winter with realistic ambitions of Classic glory.
But the dream was short-lived, with an early-season illness meaning she did not return until the Coronation Stakes in June.
A disappointing effort at the Royal meeting followed by a no-show in the Falmouth at Newmarket suggested she may be a spent force.
However, a fair second behind subsequent American Grade One winner Euro Charline at Ascot in July hinted at a flicker of life and she headed to Yorkshire as an 11-1 chance for her latest Group Three assignment.
Fitted with cheekpieces for the first time, Kiyoshi appeared much more like her old self, travelling with the panache that was the trademark of her juvenile campaign.
Spencer was sitting pretty in behind the pacesetters heading inside the closing stages and once let down, his mount showed thrilling acceleration to seal the deal by a length and a quarter from heavily-supported 15-8 favourite Bragging.
Kiyoshi is now likely to test her powers at the highest level once again in the Kingdom of Bahrain Sun Chariot Stakes at Newmarket on 4 October.
Hills said: "She is very good indeed, but she was a sick filly in the spring and had to have two months of antibiotics.
"She did a piece of work last week that was really special, quite breathtaking, and it looked like she had her old spark back inside her. We had the cheekpieces on then, so we left them on.
"It's not a definite, but the obvious place to go with her would be the Sun Chariot."
