Oju Chosan has extended his own record-breaking feats with a fifth consecutive win in the Japan's rich steeplechase, the Nakayama Grand Jump.

His fourth win a year ago gave him the outright record after he was tied on three with Australian horse Karasi who won from 2005 to 2007.

Karasi, trained by Eric Musgrove and ridden by Brett Scott, followed in the footsteps of 2002 winner St Steven who was trained by New Zealander John Wheeler but represented Australia in the race.

Oju Chosan, trained by Shoichiro Wada and ridden by Shinichi Ishigami, was the dominant favourite in Saturday's race with the meeting held in driving rain.

His win marks the first time in Japanese racing history a horse, trainer and jockey have won the same Graded race five times in a row.

The odds-on favourite was in front over the 10th and final jump and held off Meisho Dassai to win by three lengths.

"He's really a great horse. I'm grateful that he always gives his best performance," Ishigami said.

Wada admitted he was unsure before the race how the horse would go in the wet.

"I couldn't imagine how he will race as he had never raced on such a soft ground. I'm glad that he was able to race well, clearing all the jumps almost perfectly. He was able to show his outstanding power again today," he said.