Japan's incoming national coach Jamie Joseph says he expects "a lot of hard work" between now and the 2019 World Cup as he prepares to take charge of the Brave Blossoms this year.

The New Zealander, who will first oversee the Highlanders' Super Rugby title defense after steering them to a maiden championship last year, says Japan's recent successes and the exit of former coach Eddie Jones have left him with a tough task.

"There's no doubt Eddie has done a wonderful job and it's been a big loss for Japanese rugby," Joseph said ahead of the Natixis Cup match in Hong Kong between the Highlanders and French Top 14 outfit Racing 92.

"The victories against South Africa and Samoa and the US at the World Cup have made my job a lot more difficult because they've done so well. But luckily I've got three years to prepare before the World Cup (in Japan). It's going to be a lot of hard work between now and then.

"It's difficult because the player base in Japan - particularly with the quality and experienced players - isn't what I'm used to."

But Joseph believes the experience gained as more Japanese players head overseas should put the team in good stead.

In particular, he expects the Sunwolves' upcoming Super Rugby debut and top points scorer Ayumu Goromaru's move to the Queensland Reds will bolster Japanese rugby. The fullback, 29, is a cult hero in Japan after he kicked 24 points in the Brave Blossoms' 34-32 upset win over South Africa at the World Cup.

The Sunwolves join an expanded 18-team Super Rugby competition this year with their first game against South Africa's Golden Lions on February 27.

"A big reason why the Japanese team have improved is because a lot of those players have had Super Rugby experience, and they took that to the World Cup last year," Joseph said.

Goromaru's departure "will have a positive impact because he is gaining experience playing for another team and taking those experiences back to Japan."