England overcame a disastrous first half when their experimental side trailed an effervescent Japan 15-10 to turn on the power after the break and run out 35-15 winners at Twickenham on Saturday.
The long-shot outsiders had threatened a repeat of their 2015 World Cup upset over South Africa when well-made tries for Ryoto Nakamura and Michael Leitch rewarded some terrific play and a dominant 40 minutes after England had struck first through Danny Care.
Eddie Jones sent on most of his big-gun replacements in the second half and, lifted by the arrival of Owen Farrell, they made the difference as a Mark Wilson try and the boot of George Ford brought some normality to the scoreboard at 23-15 after 65 minutes.
Winger Joe Cokanasiga then marked his debut with a try and Dylan Hartley, for the second week running, was carried over by a rolling maul to give some polish to the scoreboard.