Tokyo - When South Africa take on Japan in the Rugby World Cup quarter-finals, the Springboks will be well aware of their pacy game thanks to several players having had stints in the Japanese Top League.

Established in 2003, the Top League comprises 16 teams mostly owned by large corporations.

Well funded and able to entice marquee players, it has successfully attracted a host of stars notably from Super Rugby, giving it a wider profile in a country where professional football and baseball dominate.

"The club teams do everything at 100mph: training, fitness, the guys don't rest. It's a fantastic work ethic on and off the field, a fantastic culture," said Springbok No 8 Duane Vermeulen.

Vermeulen is on the books of Kubota Spears, with the Top League this year also featuring the likes of ex-All Black great Dan Carter (Kobe Kobelco Steelers) and Australian star Matt Giteau (Suntory Sungoliath).

"I really enjoyed it," current Bok fullback Willie Le Roux said of his two seasons with the Canon Eagles, having signed from English Premiership team Wasps for Toyota Verblitz post-World Cup.

"It's very open. If I had to describe it, it's like sevens in a 15-man game. It's very quick, you run from everywhere.

"Sometimes there's not much structure, so everyone just plays what they see. It was quite fun, enjoyable."

On the coaching side, assistant Springbok coach Matt Proudfoot described his time at Kobe as a "great learning experience".

"I got to coach different types of players and understand their mind-set," he said.

Lock Franco Mostert currently plays for Gloucester after turning out for the Ricoh Black Rams.

"If you look at the Top League, it's not that much different from South Africa, probably not so physical but a bit quicker," Mostert said.

"They have worked very hard for what they want."

The number of Springbok players to have appeared for teams in Japan is staggering, offering a wealth of inside information on a nation on the rise.

Japan were the surprise inclusion in the quarter-finals, having topped Pool A with four wins from four, including victories over Six Nations giants Ireland and Scotland.

They racked up a shock victory over the Boks in pool play in the 2015 World Cup, but Vermeulen said that now counted for nothing.

"What's better than playing the host country in the quarter-final? That's definitely something you have to embrace and I'm looking forward to it," said the former Bulls and Toulon forward.

"I play my club rugby here and in a way, I really kind of enjoy it. I love the country, the food, the culture."

Japan, Vermeulen added, brought a "different style of play, it's not something you're used to".

Vermeulen said the Boks, particularly those who play or have played in Japan, knew what was coming but "you've still got to pitch up on the day."

Three South African-born players made the Japan squad for the World Cup: Lappies Labuschagne and Wimpie van der Walt, who have both been based in Japan long enough to have earned citizenship, and star winger Kotaro Matsushima, born in Pretoria to a Zimbabwean mother and Japanese father.

"I've played against some of them in Super Rugby and with and against them in the Japanese Top League," Vermeulen said.

"Lappies is in the top four tacklers at World Cup so far. They're guys who are earning respect week in, week out. It's going to be tough on Sunday coming up against them."

Joining Vermeulen, Le Roux and the raft of other South Africans in Japan next season will be a host of All Blacks: Kieran Read (Toyota Verblitz), Ryan Crotty (Kubota Spears), Liam Squire (NTT Docomo Red Hurricanes), Sam Whitelock (Panasonic Wild Knights) and Brodie Retallick (Kobe Kobelco Steelers) have all succumbed to the lure of the yen.

Australians will also be well represented with current Wallabies Samu Kerevi (Suntory Sungoliath), David Pocock (Panasonic Wild Knights) and Will Genia lining up alongside former Reds half-back partner Quade Cooper at Kintetsu Liners in Tokyo.

Teams:

Japan

TBA

South Africa

15 Willie le Roux, 14 Cheslin Kolbe, 13 Lukhanyo Am, 12 Damian de Allende, 11 Makazole Mapimpi, 10 Handre Pollard, 9 Faf de Klerk, 8 Duane Vermeulen, 7 Pieter-Steph du Toit, 6 Siya Kolisi (captain), 5 Lood de Jager, 4 Eben Etzebeth, 3 Frans Malherbe, 2 Bongi Mbonambi, 1 Tendai Mtawarira

Substitutes: 16 Malcolm Marx, 17 Steven Kitshoff, 18 Vincent Koch, 19 RG Snyman, 20 Franco Mostert, 21 Francois Louw, 22 Herschel Jantjies, 23 Frans Steyn