Before founding Chartmetric, Sung was a founding member of Gamevil, one of South Korea's leading game companies. He jumped into the Korean game industry before it was fully established and led the company's growth alongside the industry's development. However, not content with just the company's success, Sung aimed to fulfill his dream of building a career and starting a business in Silicon Valley. Approaching his 30s, he left Gamevil and started anew as an intern at Sun Microsystems in Silicon Valley. While working at Sun Microsystems, the company was acquired by Oracle, naturally transitioning his career to Oracle. Yet, he chose to step out of his comfort zone for another challenge.

After leaving Oracle, Sung faced numerous challenges before finally starting Chartmetric in 2015. The company has since been steadily growing, as evidenced by its increasing ARR and other metrics.