Single Dad in Love

The love story of a single dad, Kang Poong Ho, who raises his 7-year-old son alone after being abandoned by his first love, Yoon So Yi. By day, he works as a pest exterminator, and by night, he is a martial artist. Jeon Ha Ri is a medical student from a wealthy family who falls for Poong Ho. She secretly teaches Poong Ho's son, San, how to play the piano. Poong Ho's first love is also his son's mother, who is a cold and proud woman who left her family to study abroad as a pianist. She was sponsored by Jeon Ki Suk, who happens to be her fiancee and Ha Ri's father.
(Source: DramaWiki)