Ramjet third, Dura Erede fifth in Korea Cup.
Diktaean, the 7-year-old from Japan's local circuit, won his first international title in the Korea Cup that followed the Korea Sprint as the eighth race on the card.
The Oi-based gelding trained by Katsunori Arayama came off the pace from the middle of an 11-horse field to go under in 1 minute, 50.8 seconds over the 1,800m on dirt.
The JRA's Ramjet and Dura Erede followed Diktaean to take third and fifth place, respectively.
Ramjet broke free first down the stretch with Hong Kong's Chancheng Glory right on the heels of the 4-year-old colt. But as the two went toe to toe and Chancheng Glory, under Chun Lok Chau, began to pull away, Diktaean charged hard from the outside to close by one full length.
Ramjet crossed the finish line another two lengths back. Dura Erede was further behind, trailing home an additional 10 lengths.
The winning jockey, Takayuki Yano, was over the moon over his success aboard the King Kamehameha son out of the dam Medeia.
"I'm so grateful," Yano said during the post-race interview. "It's my third time riding in Korea and I count my lucky stars for having the opportunity to ride in a race as big as this.
"I'm really glad we managed a result. We owe it to so many people. I'm thrilled we won and I hope I can come back to Korea.
"We were in a small field which allowed us to grab the position we wanted and make our move when the time was right."
The winner's check was 800 million won (88 million yen). Diktaean started his career with the JRA and only moved to the NAR earlier this year.
The Korea Cup earned international graded status in 2022 with Crown Pride from Japan winning the race back-to-back the last two years.