The 2017 world champion saw off China's Shi Yu Qi to set up clash with surprise semi-finalist Kevin Cordon
The world number two defeated China's Shi Yu Qi in straight sets, 21-13, 21-13, on Saturday (31 July) at the Musashino Forest Sport Plaza.
Axelsen who is seeded third in the tournament is now just one win away from guaranteeing he improves on the bronze he won at Rio 2016.
The 2017 world champion will next play surprise semi-finalist Kevin Cordon from Guatemala for a place in the final.
The match will take place on Sunday, 1 August at 1300 JST.
The Danish world champion reveals how speaking Mandarin has opened up opportunities for him in the world of badminton.
Axelsen in control
The Dane who is making his second Olympic Games appearance, was in complete control throughout the 41 minute encounter against Shi.
Axelsen took an early lead in the first game and the Chinese player was unable to find a response. After the mid-game interval, the Dane found another and gear surged ahead to clinch the opening game.
Shi who won gold at the Nanjing 2014 Youth Olympic Games kept closer to his opponent at the start of the second game, but once again, the 2017 world champion picked up the pace after the halfway point to run away with the game and confirm his spot in the final four here in Tokyo.
2021 Getty Images
The 34-year-old Cordon is enjoying a fairytale run at his fourth Olympic Games outing, having already seen off several players who are ranked higher than him.
Cordon has two Pan American Games gold medals and his best result at the world championships was in 2011 when he made it to the quarter-finals.
Viktor Axelsen will next play Kevin Cordon in the second men's singles semi-finals on Sunday (1 August) which starts from 1pm local time.