Japan’s classic season began on Sunday when fifth favourite Let's Go Donki won the G1 Oka Sho (1000 Guineas) for fillies at Hanshin.

Trained by Tomoyuki Umeda and ridden by Yasunari Iwata, the front-running filly led the 18-runner field before sprinting clear turning for home to score by four lengths.

The odds-on favourite Rouge Buck could finish only ninth in the ¥208 million contest.

"No-one was taking command so I let my filly go up front," said winning jockey Iwata.

"It was a good move because she was able to travel at an easy pace. She stretched well after saving energy in the first half of the race.”

“She's been winless after breaking her maiden but had very close finishes so I'm glad she was able to demonstrate her true strength."

Let’s Go Donki had registered a second in the G1 Hanshin Juvenile Fillies and third and a second in the G3 Sapporo Nisai Stakes and the G3 Artemis Stakes after breaking her maiden in her debut last August as a 2YO.

She launched the current season with a third in the G3 Tulip Sho in March.

It was the first Japanese G1 win for trainer Tomoyuki Umeda, who captured the Caulfield Cup with Admire Rakti last October.

Melbourne Cup winning jockey Iwata has now won 24 JRA G1 races including his first Oka Sho title with Gentildonna in 2012.