World Rugby said the record represented a TV audience share in excess of 64 per cent and "is another strong indicator that the awareness and popularity of rugby is growing there (Japan) as it prepares to host Rugby World Cup 2019."
TV numbers are also huge in England, Wales and Ireland, buoying broadcasters.
Ireland's three pool games have pulled in big numbers including 758,000 on TV3 for the Sunday afternoon game against Romania.
And even though they lost to Australia and Wales, England's match against the Welsh was a victory for ITV after it helped the broadcaster destroy the BBC audience for the popular Dr Who programme.
ITV exterminated the Daleks with an audience of more than 10 million compared to just 3.7 million for Dr Who - its lowest ranking since the series was rebooted in 2005, although the broadcaster faces a tough task retaining big audiences now host team England is out of the tournament.
ITV and World Rugby will be hoping the glamour of the All Blacks will help in England's absence, although Steve Hansen's men have been barely a blip on the international ratings radar since the event started.
New Zealand's weak pool featuring Argentina, Georgia, Tonga and Namibia hasn't helped, robbing the All Blacks of any compelling contests that would draw viewer attention like the so-called "Pool of Death" with the likes of England, Wales and Australia. The All Black matches have featured well down the list in ratings among worldwide broadcasters.
But that will change once the knockout phases of the tournament start next week and ITV and other national broadcasters, including SKY TV in New Zealand, will be hoping for boosted figures. Germany has been the surprise TV performer. Despite not even having a team in the tournament, more than 300,000 viewers watched the tournament opener between England and Fiji. In comparison, 230,000 people watched that opening game in rugby-mad New Zealand on SKY Sport 1 and another 182,000 on Prime. World Rugby say more than 2.6 million Germans watched the first three games screened, forcing broadcaster Eurosport to increase the number of games it planned to show.
The All Blacks v. Georgia game last weekend has blitzed all other Rugby World Cup games so far in terms of television viewership numbers in New Zealand.
There were more than 441,000 viewers for the 8am Pool C fixture on SKY Sport 1 on Saturday, so far the most time-friendly All Blacks game of the World Cup.
This means 10.5 per cent of all people aged five years and older in New Zealand watched the All Blacks beat Georgia 43-10.
Delayed coverage of the game on Prime later that day saw more than 135,000 people making the most of the free-to-air coverage.
Telecommunications company Spark also noted a significant rise in data use on its mobile devices during the game.
It saw a 44 per cent increase in 4G data use from 8am to 11am compared with the average of what is normally used at that time across the week.
During the All Blacks and Namibia game on September 25, there was also a 37.5 per cent increase from 6am to 9am. Peak data use from 7am to 8am was also higher than any other point that week.
Spark spokeswoman Lucy Fullarton said the increase is driven by two kinds of behavioural changes that Spark had seen emerging over the past few years.
People were now often streaming the games on their mobile device or following live commentary on certain news or sports websites, she said.
"That's the first thing, the second thing is we're seeing that people want to engage with their friends and family during the game. They're not just watching it passively anymore."
Ms Fullarton said this kind of interaction could be via online messaging services like Whatsapp, or on social networking sites like Facebook.
"They want to be able to instantly comment and get that response from their friends around the same event during the game."
Spark had also noticed a general spike in the amount of text messages sent, mainly during half-time and before or after games.
"Minutes not so much," Ms Fullarton said. "Although, again, half-time or before or after games we see a bit of a spike. People don't really want to talk on the phone while they're watching the rugby."
Meanwhile, the Australia v. England game at 8am on Sunday morning on SKY Sport 1 was the next most-watched World Cup fixture of the weekend.
The Pool A game, which saw hosts England crash out of the tournament in dramatic fashion, had more than 364,000 viewers - or 8.7 per cent of all people aged five years and older.
The two earlier games that morning, between Samoa and Japan and South Africa and Scotland, had more than 31,000 and over 50,000 viewers respectively.
A replay of the Samoa and Japan game directly after the England v. Australia clash attracted over 143,000 viewers on SKY Sport 1.
The two live games on Monday morning - Argentina v. Tonga and Ireland v. Italy - failed to generate more than one per cent of all people aged five years and older in New Zealand.
The earlier game between the Argentines and Tongans had over 11,000 viewers (0.3 per cent), while the Irish and Italians had more than 23,000 (0.6 per cent).
The figures are sourced from Nielsen TV Audience Measurement (TAM) AP5+ and are based on a national audience of 4,200,880.
