But once the World Cup loot is counted in 2019 by the IRB and backs are slapped for a job well done, what will be the prognosis for rugby in the ensuing years? Will hosting a hugely successful World Cup make any difference to the standing of the game? Will Japan benefit to the extent that they fulfil their stated ambition of becoming a top 10 side?
This is where the picture becomes murky. In all likelihood, hosting the World Cup won't make a blind bit of difference to the standing of rugby in Japan. Yesterday's test, despite selling out quickly, had little traction in Tokyo. Main sponsor AIG had dolled up much of the city's Ginza Line on the Metro with black paraphernalia but the place is so gargantuan that news of the All Blacks' arrival probably didn't reach 99 per cent of the population.
A handful of players, including Richie McCaw, were sent out to sign autographs at an adidas store next to the famously busy Shibuya Station: the iconic road crossing is considered the busiest intersection in the world. Even with such a weight of humanity in the vicinity, the shop was, at best, half full.
None of this can serve as hard evidence that the game has no chance in Japan but it is probably indicative of the battle rugby faces. The sport is not ingrained across the populace. Baseball is the sport of the people, followed by football. Rugby's origins in Japan lie in the universities. It is a sport for the educated elite and, with its unfathomable rules, it's not the sort of game the uninitiated can take to easily.
The biggest problem of all, however, is that Japan's national team, for all their bravery, speed, skill and tenacity are never going to be a Top 10 nation. They appear to be prisoners of their genetic base.
What hope did they truly have yesterday when the tallest man in their side, Hitoshi Ono, was 1.92m? Even with a step ladder, he'd have done well to get lineout ball from Dominic Bird.
No side can realistically hope to win against the best if they are giving away so much weight and height per man. Frank Halai, 1.95m and 110kg, was marked yesterday by Kenki Fukuoka, who is 1.73m and 82kg.
No one should pretend that revolution is on the cards, that the last week was the start of a new era of regular tests between Japan and the All Blacks. If it is, it will only be because the All Blacks are filling their pockets with cash in the process.
So the World Cup will not do much - despite the hype and feel-good statements that will gush from the IRB - to shunt Japan up the pecking order; without regular victories against the best, they won't win the audience they crave.
No one directly involved in the game is actually going to tell it like it is. The myth will be perpetrated because Japan is rich and New Zealand, and many other countries, fancy that they could benefit from that wealth.