Japan coach Jamie Joseph promised the hosts would "give 150 percent" to hit their target of reaching the Rugby World Cup quarterfinals after naming his 31-man squad on Thursday.

The Brave Blossoms will be at full strength when they face Russia in the tournament's curtain-raiser in Tokyo on September 20 after talismanic captain Michael Leitch returned from injury at the recent Pacific Nations Cup.

"The team has set a goal of making the top eight for the first time in the history of Japanese rugby," Joseph told reporters.

"The staff and players will give 150 percent - whether that's enough only time will tell."

"Our game is based around speed, skill and structure," added the former All Black. "But the key difference this year is we are fit enough now to play that game. We're training at a level of intensity that's 25 percent higher than our matches - I think that's our key weapon."

Japan famously won three games at the 2015 World Cup under Eddie Jones, including an astonishing 34-32 victory over two-time champions South Africa.

Currently ranked ninth in the world after capturing their third Pacific Nations title, the Japanese also take on Ireland, Scotland and Samoa in Pool A as they target a place in the knockout stage for the first time.

They will be boosted by their success at the Pacific Nations, where they beat Fiji (34-21), Tonga (41-7) and the United States (34-20).

Leitch's return from a lengthy injury also helps Japan's cause as they look to go one further than at the last World Cup.

"When I arrived in Japan the question was thrown at me how I could take the team to the next level after the success Eddie had," said Joseph.

"The challenges were increasing player depth, to develop players in time for the 2019 World Cup and to create a winning mentality."

"Four years later we have played every tier-one team and we've had four seasons of Super Rugby," he added.

"That's helped toughen up the players. I confidently say we are one team as we go into the World Cup."