The 63-year-old if successful would deliver the race the Japanese consider the Holy Grail of the sport and which they have been trying to win since Speed Symboli tried his luck in 1969.
Yahagi has staked a lot on his three-year-old, persuading owner Susumu Fujita to splash out the princely sum of 2.1 million euros ($2.3 million) for Shin Emperor at the sales in Deauville, France, in 2022.
Yahagi's mind was on the Arc when he targetted Shin Emperor, not least because he is the brother of French-trained 2020 Arc winner Sottsass.
Like Sottsass, Yahagi used the Irish Champion Stakes last month as his prep race and he emerged with huge credit finishing third.
"I have wanted to win the Arc for fifty years now," he said through a translator at a press conference on Friday.
"I have been dreaming about it and now I am very emotional to be in France and having a runner.
"For the Japanese it is a very, very important race, and is becoming more and more important."
Shin Emperor's jockey Ryusei Sakai -- who teamed up with Yahagi to finish third in this year's Kentucky Derby with Forever Young -- won on his first ride in France but admits the Arc challenge is on a totally different level.
"The Arc is the dream of everyone in Japan," the 27-year-old said.
"I am very emotional to ride in it this year as every jockey dreams of riding in the Arc.
"A lot of fans are encouraging me to win it and I have to meet their expectations."'A miracle'
Yahagi, who has had one previous runner in the Arc Stay Foolish who finished 14th in 2022, has won races all over the world except in Europe.
Indeed he already made turf history in becoming the first Japanese trainer to win at the United States's most important meeting the Breeder's Cup in 2021.
It was a double no less with Loves Only You and Marche Lorraine in the Filly and Mare Turf and Distaff respectively.
However, he says there is a good reason why no horse from outside Europe has yet to be crowned Arc champion.
"The Arc is the summit of all races," said Yahagi, known as 'the man with the hat' and on Friday donned a red one.
"It is the most difficult race to win.
"It is a very European race, the distance 1 1/2 miles (2400 metres) and the ground (usually soft) is why all the winners are from Europe.
"Those are the reasons why it has been complicated for us and that is why I have brought over this French bred horse."
Yahagi -- who along with Sakai warmed up for the Arc with a victory with Breeder's Cup Classic bound Forever Young on Wednesday in Japan -- said even getting to the Arc was an achievement.
"When I bought this horse I dreamt of bringing him here for the Arc," he said.
"However, the percentages of developing him into a star and then to the Arc are very slim.
"It really is a miracle to be able to bring him here.
"Thanks to my efforts and those of Mr Fujita and the jockey in getting him here we have already achieved a miracle."
Yahagi was nonchalant about what it might do to his image in Japan if Shin Emeror breaks the Arc glass ceiling.
"It should not be too much of a change," he said.
"Maybe I won't be able to take my train unbothered," he chuckled.
