Bharadwaj beat Germany's David Peng 11-6 11-4 11-8 in a 20-minute men's singles match, while Kuhoo and Arjun defeated Pawel Smilowski and Magdalena Swierczynska of Poland 11-7, 11-9 and 11-3 in mixed doubles event to reach the final four.
Bharadwaj will face Turkey's Muhammed Ali Kurt, while Kuhoo and Arjun will next take on Scotland's Adam Hall and Julie Mc Pherson.
Belgian Junior open is one of BWF's sanctioned events which is testing out the experimental scoring system -- 5 games to 11.
Kuhoo and Ningshi Block Hazarika had lost 9-11 3-11 5-11 to second seeds Eva Janssens and Yvonne Li of Germany in the women's doubles event.
Earlier this month, both Kuhoo and Arjun had won two gold medals in Sushant Chipalkatti Memorial Junior International Badminton Championship at Pune.