The sport is enjoying a surge in popularity in the country that will host the next World Cup in 2019 and after securing a franchise in the Super Rugby tournament, Lapasset believes a similar deal at international level is a distinct possibility.
Japan beat off a bid from Singapore to enter next year's expanded 18-side tournament and will get their first taste of Super Rugby action at the Prince Chichibu Memorial Stadium in Tokyo on Feb. 27 when they host the Lions of Johannesburg.
"Japan is part of the total global vision of the rugby that we are promoting in the world, especially in the South with Argentina, South Africa, New Zealand, Australia," Lapasset told reporters in Tokyo on Monday.
"That's the top five -- with Japan. Not just Tier 2 and Tier 1, the top five," the Frenchman added.
"We need to achieve the process that all five will be pushing together to develop the southern competition and to promote the best rugby ever that we can do in the South.
"We did the same in the North with the Six Nations. Now it will be the five nations in the South."
The popularity of rugby in Japan has rocketed after the Brave Blossoms stunned two-time world champions South Africa with a last-gasp 34-32 win at the recent World Cup in england.
They went on to become the first team to bow out of the pool stages with three wins but had better luck in completing a second-half rally against hosts Hong Kong on Sunday to book a berth at the 2016 Olympic rugby sevens tournament in Rio.
Television viewing figures in Japan soared after the South Africa game and Lapasset has fixed his sights firmly on increasing the sport's popularity across the rest of Asia.
"The Super Rugby is a good format to promote rugby in the South that includes some matches in Singapore. That's important to extend the value and the quality of the game in Asia," he said.