Senor Toba set out to make all in the 12-furlong contest, with William Buick setting in second aboard the Andre Fabre-trained Botanik while Ryan Moore and Stone Age, who is trained by Aidan O'Brien race keenly on his heels in third.
It looked as though Buick was in prime position in the straight when Senor Toba began to back pedal, but Damien Lane was lining up Win Marilyn for her run, sweeping round the outside of the field.
Fellow Japanese runner Glory Vase, who was bidding for a third successive win in the race, tried to go with her, but Win Marilyn was just too strong.
Botanik held on for second, with Glory Vase third and Stone Age fifth. His fellow O'Brien inmate Broome failed to figure in the finish, coming home eighth.
Win Marilyn trainer Takahisa Tezuka said: "After the Queen Elizabeth II Cup, we got together and unanimously decided to target this race.
"The mare was at her optimum trip and Damien gave her the perfect ride.
"It's my first winner here and I'm incredibly proud."
Lane added: "I'm breathing a sigh of relief to break my duck here. She showed such a good turn of foot in the QEII when I thought the horse that beat us was something special.
"I'm proud to be a part of Japanese racing and getting on good horses like her."
Buick was a late replacement for Mickael Barzalona aboard the Godolphin-owned Botanik and he was impressed with the four-year-old's effort.
"He's run a blinder, he's a lovely horse," said Buick. "To be honest, if you ignore his run on Arc day, he looked like he had a real chance.
"Mr Fabre doesn't send many horses here and when he does send them you know they have a chance.
"He's Mickael's ride and unfortunately Mickael has Covid, so I'm only a step-in. But he's going to be a really nice stayer for next year. He's got a great attitude and he stayed well the whole way."
O'Brien will consider future plans for his runners now.
He said: "It didn't happen today but we will go away and have a think about what they might do next year. There are a lot of races for them."
Another French runner, Bubble Gift, finished sixth while German contender Mendocino reared as the stalls opened and lost any chance.