Retallick scored the first of five All Blacks tries, while 13 points came from the boot of Richie Mo'unga.\
Foster was content with the way New Zealand dug in to see off the Brave Blossoms.
"I thought it was a day where we could have panicked a little bit," he said.
"But I thought they hung in there well and did what they needed to do at the right time."
Japan will now prepare to do battle with England at Twickenham on November 12 and head coach Jamie Joseph is relishing what he expects to be a bigger challenge.
He said: "The key for us really is to go to England now and replicate that performance against a better side."