Harshana claimed a bronze medal in the Under 7 age category at the 2009 Asian Schools Chess Championship which was held in Sri Lanka. He also claimed gold medal in Under 11 age category at the 2014 World Schools Chess Championship which was held in Brazil. He was awarded the Candidate Master title in 2015. He claimed silver medal in Under 13 category at the 2016 World Schools Chess Championship which was held in Sochi, Russia. He also won silver medal in Under 15 category at the 2018 World Schools Chess Championship which was held in Albania. He also won gold medal in Under 16 open category at the 2018 Commonwealth Chess Championship which was held in New Delhi. In the same year, he was awarded the FIDE master title. He also competed at the 43rd Chess Olympiad which was held in Georgia in 2018 where he scored 6 points from 10 matches.