The recalled Gloucester wing, winning just his second cap, seized his chance to stake a claim for a place in England coach Steve Borthwick's squad for next year's Rugby World Cup in Australia in style.
The younger brother of former England international Jonathan Joseph, Will struck as early as the opening minute.
England crossed Japan's line eight times in a first half that finished with Borthwick's team out of sight at 49-10 and Joseph having run in four of England's eventual 13 tries.
An utterly lopsided encounter saw England post both their highest score and record-winning margin against Japan, surpassing a 60-7 success at the 1987 Rugby World Cup in Australia.
Joseph had a hat-trick inside an opening quarter when England scored five tries as they capitalised on a man advantage after Japan lock Harry Hockings was given a 20-minute red card for a high tackle on Ellis Genge.
And when Joseph went over in the 57th minute off an intercept, he became just the fifth player to score five tries in a Test for England after Douglas Lambert, Rory Underwood, Josh Lewsey and Henry Arundell.
England kicked off having made 10 personnel changes to the starting side that overwhelmed Australia 45-22 at Twickenham last weekend ahead of next week's clash with New Zealand.
Henry Pollock was in at No 8 after scoring two tries off the bench against the Wallabies having replaced injured wing Immanuel Feyi-Waboso at half-time.
Japan had started heir November campaign with a narrow 28-21 loss to Wales.
That result was put into a fresh light by Wales's stunning 35-28 defeat of New Zealand - their first win over the All Blacks in 73 years - in Cardiff earlier Saturday.
Japan coach Eddie Jones, a former England boss who gave Will Joseph his Test debut, had vowed the Brave Blossoms would "play the house down".
But it was England who did just that with Joseph speeding, skipping and fending his way down the right touchline in under a minute.
George Ford, who had a poor day off the kicking tee, could not convert but it scarcely mattered.
To make matters worse for Japan, Hockings was sin binned for a high shot on Genge before the second row's punishment was upgraded to a 20-minute red card on review.
Joseph then went over for his second try, touching down in the right corner after an excellent grubber kick behind the defence from recalled full-back Freddie Steward.
Naoto Saito's penalty got Japan on the scoreboard but this was merely a brief interruption to England's try-fest.
Steward went in off a short pass and Genge powered over before Joseph joined Jonathan - who scored two England hat-tricks, in 2016 away to Italy and at Twickenham in 2017 against Scotland at Twickenham, - in grabbing a Test match treble.
That meant they became the first brothers to score hat-tricks for England, before the 24-year-old Will, 11 years younger than Jonathan, went one better with an acrobatic one-handed dive.
England wing Cadan Murley crossed out wide before Japan co-captain Warner Dearns pulled a try back from close range.
But it was England who had the final try of the half when Ben Earl was driven in off a maul.
England lock George Martin powered over in the 44th minute before Opeti Helu scored for the visitors.
But then came Joseph's fifth try, with replacements Ben Curry, Marcus Smith and Greg Fisilau piling on the agony for Japan.