The spirit of co-operation in pursuit of spring riches on foreign soil has been obvious.

But it's time for Japanese thoroughbreds Chestnut Coat and Sole Impact to go from travelling companions and training track workmates to Caulfield Cup rivals.

Chestnut Coat and Sole Impact are chasing a second Caulfield Cup win for Japan after Admire Ratki scored under Zac Purton in 2014.

Before Admire Ratki there was a Japanese quinella in the 2006 Melbourne Cup when Delta Blues edged out Pop Rock.

It was supposed to be a start of a Japanese domination of the Caulfield and Melbourne Cups.

But extended quarantine restrictions put an end to that prediction until a relaxation in Japanese protocols led to Admire Ratki's triumph.

Chestnut Coat is the more favoured of the latest duo, the first Japanese-trained horses in three years to run in the Caulfield Cup.

In the hands of Yoshito Yahagi, Chestnut Coat has undergone a faultless preparation.

"I'm really satisfied with how he's been training here and he's in excellent condition," Yahagi said.

"Hopefully now he can run a good race."

Sole Impact has been a big part of trainer Hirofumi Toda's training career after being spotted soon after being foaled.

Toda has spent the majority his stay at Werribee with Sole Impact and said the horse had adapted well to the weather in Melbourne.

"The horse has been improving a lot and I'm happy about that," Toda said.

"The jockey galloped him two days ago and he told me the horse is feeling well and I got on him this morning and he tells me he's feeling well too."

Sole Impact will be ridden by Ryusei Sakai, one of only two apprentices in the $5 million race.

Sakai is apprenticed to Yahagi and was sent to Melbourne 12 months ago to hone his craft.

He spent time at Flemington with Troy Corstens and Phillip Stokes in Adelaide before a trip to Dubai to help prepare the Yahagi-trained Real Steel, a minor placegetter to Benbatl in the Dubai Turf on World Cup night.

Sakai returned to Ryan Balfour in Adelaide.

"I've been studying riding while I've been here," Sakai said.

"I was rusty when I first started but I've been getting lots more rides and my riding has improved."

Sakai's latest Australian stay is almost complete as he returns to Japan and back riding for Yahagi next month.