New Harlequins prop Mike Worsley scored the tourists' first try of the day early on when he crossed the line from short range, ensuring that England were never behind their hosts on the scoreboard, leading 24-10 at the interval.
A try from Namba for the Japanese after some good forward work in the tight kept the game open as a contest, but the intervention of Balshaw from fullback saw the visitors accelerate away.
He intercepted and ran nearly the whole length of the pitch for one of his scores, as well as setting up a try for prop Will Green with a well-judged kick.
England ran in nine tries in total as their strength told late on, with three of them coming from props – Neal Hatley adding to Green and Worsley's tries.
New Bath scrum-half Martyn Wood helped himself to a pair of tries as the field opened up in hot and humid conditions.
Gloucester wing James Simpson-Daniel and Saracens centre Ben Johnston were the other try-scorers in a game which showed the growing strength in the English game.
The England side was based on the same second-string outfit which claimed the Churchill Cup title in Canada last month, as well as getting the better of a Japan Select XV on Thursday.
But Japan dug in and never gave up, their effort being rewarded right at the end when replacement Takashi Yoshida crossed the line – Hirose converting for the second time after previously strikng two penalties.
For Japan:Tries: Yoshida, NambaCons: Hirose 2Pens: Hirose 2
For England:Tries: Balshaw 2, Wood 2, Simpson-Daniel, Johnston, Worsley, Green, HatleyCons: Walder 5