De Minaur was up 6-4 3-2 with a break of serve when Hurkacz pulled out while down 40-0 in the sixth game of the second set, after showing mobility problems.
The No.9 ranked de Minaur will now pursue a 12th career title in the final against the winner out of sixth seed Novak Djokovic and the third-seeded Daniil Medvedev.
Passage to Tuesday's decider continued a strong turnaround for de Minaur after his tournament looked in doubt 24 hours earlier.
On Sunday the 27-year-old was in dire trouble in his quarter-final against Russia's Andrey Rublev after winning only one game in the first set, but came back to win 1-6 6-2 6-3.
Monday continued the Australian's sparkling form, though world No. 34 Hurkacz made him earn the win, despite coming in trailing de Minaur 3-1 on career meetings.
De Minaur pounced immediately to break a tentative Hurkacz in his opening two service games before holding to lead 4-0, and again for 5-1.
To his credit, Hurkacz steadied and after breaking back from deuce in the eighth game he held again to 15 to make it 5-4.
De Minaur steeled himself, however, holding serve to 15 to take the set.
Another break in the third game of the second set helped de Minaur build a 3-1 lead.
Hurkacz fought desperately to hold serve in the following game - surviving four break points and a marathon deuce game - to make it 3-2.
But he would see only three more points before withdrawing.
In Tokyo, defending champion Carlos Alcaraz overcame early wobbles on his serve to outclass fellow Spaniard Jaume Munar 5-7 6-3 6-1 and reach the Japan Open final, taking another step towards his first singles title after his comeback from a wrist injury.
Alcaraz completed the career grand slam by capturing the Australian Open title in February but sustained the injury two months later.
He only came back at the US Open, where a quarter-final run hinted at a swift return to form.
The 23-year-old, who moved through the gears during Team Europe's triumphant Laver Cup campaign in September, was cruising against Munar in Tokyo at 5-4 before gifting the opening set to his opponent with two shaky service games.
After a sluggish start to the next set - completing a run of 16 straight losing points - Alcaraz raised his level to force a decider and the seven-time major champion wore Munar down with stunning shot-making to set up a title clash with either Jiri Lehecka or Valentin Vacherot on Tuesday.
