After a rousing opening ceremony and passionate pre-match challenges, the All Blacks drained all the tension and anticipation by scoring four tries in the first 33 minutes, and finding the Tongan defence wanting out wide.
But after taking a 29-3 lead into halftime, New Zealand failed to capitalize on long periods in Tonga's half by giving away penalties against their prideful Pacific neighbours and dropping crucial passes.
While there wasn't a signature moment to kickstart the tournament like John Kirwan's 80-meter try against the Italians the last time New Zealand opened the cup on home soil in 1987, a host nation starved of another cup triumph could feel satisfied to move one win closer to a second title.
"It was a start, I think that's all we can look at it as," All Blacks captain Richie McCaw said. "There were definitely some good patches. Perhaps in the second half, we spent a bit of time in their 22 and we didn't actually capitalize.
"I thought we brought physicality, our defence was reasonably good. It was a bit disappointing to let them score but we had to defend for a while."
McCaw said after the frantic start, the All Blacks let themselves down.
"It's easy to get a bit loose," he said. "Perhaps we just expected it to happen, especially as we made breaks and weren't ruthless. That's a bit disappointing.
"We're just excited about getting under way tonight, it's a long time coming."
Tonga's renowned physical threat was negated by a more aggressive New Zealand defence which didn't concede Tonga's sole try until near the end, and only after a long, sustained assault.
Fullback Israel Dagg, selected ahead of 98-test veteran Mils Muliaina, and winger Richard Kahui both scored a pair of tries in a dazzling 22-minute period of the first half, but only Jerome Kaino and Ma'a Nonu crossed in the second. Tonga replacement prop Alisona Taumalolo burrowed under the All Blacks forwards in between New Zealand's last two tries.
"I think the ABs started very well. Every time we made mistakes they scored points," said Tonga skipper Finau Maka. "The boys came out in the second half firing, and I thought we defended well. We showed we can defend well and score a try against the best team.
"With the World Cup, I think momentum is important and we take a lot of positives from this game and look forward to the next game against Canada on Wednesday."
The 60,214-strong crowd was primed for a show from the All Blacks, to cap a spectacular curtainraiser.
A ceremony featuring bare-cheeked Maori warriors, silver sails, Jonah Lomu, and a 100-man scrum choreographed to a high-tech light show and thousands of cellphones elevated the crowd's mood, but the hoped-for clash between the All Blacks' haka and Tonga's sipi tau didn't happen because New Zealand waited for the Tongans to finish their war dance before responding with their own. Still, both were as fiery as usual.
New Zealand continued to show patience from the kickoff. New Zealand spread its attack from left to right and back and earned its second penalty close enough for Dan Carter to throw the ball over the crossbar. But he kicked it.
In the 11th minute, Carter sent Kahui crashing through the line, and the break finished with Tonga out of defenders and Dagg scoring.
Sonny Bill Williams, surprisingly selected at centre, produced one of his patented offloads for Toeava, who fed Kahui for the converted try and 15-0.
Moments later, when an All Blacks try was disallowed because Carter was shielded by teammates, a cooling crowd started doing Mexican waves, a sign they were lacking entertainment on the pitch.
So the All Blacks obliged with Williams one-handing a pass just before he hit the ground for Dagg to score his second. Four minutes later Dagg tied up two defenders and reverse-flicked to Kahui, who beat two defenders to post his second try.
The second half disappointed everyone except Tonga, whose coach, former All Black Isitolo Maka, punched the air when Taumalolo scored under a pile of bodies.
The All Blacks face Japan next Wednesday in Hamilton, happy to move on without anymore serious injuries.