Kingsbury has won six straight World Cup season titles, but won his first Olympic gold on Monday.
Since winning the silver medal four years ago, the 25-year-old from Deux-Montagnes, Que., has dominated the moguls circuit.
Kingsbury booked his ticket to the final 12 with a score of 81.27 in his first run.
The Japanese skier produced an impressively controlled run but had to settle for the bronze medal with a score of 82.19.
Rounding out the field at Phoenix Park was fourth-placed Marc-Antoine Gagnon of Canada, American moguls specialist Casey Andringa in fifth, and Norway's Vinjar Slatten bringing up the rear.
Earlier in the competition world champion Ikuma Hiroshima, bowed out just before the final round after losing control on his first jump.
Graham then produced a fantastic run to become the man to beat.
Only one would better his score and it was the overwhelming favourite for top spot on the podium, Mikael Kingsbury. The Australian managed to hold on to the position when Japan's Daichi Hara fell 0.38 points short on his final run.
Kingsbury's victory extended Canadian dominance of this event, after compatriot Alexandre Bilodeau's gold medals at Vancouver 2010 and Sochi 2014.