Speed Scandal (2008) on Netflix

Plot summary

Hwang Jeong-nam has been sending stories about raising a son on her own to the radio station where Nam Hyeon-soo works, and says she intends to find her father. She arrives at Hyeon-soo's apartment with her boy, Ki-dong, and tells the former teen idol, now in his thirties, that she is his daughter. She gives her real name as Jae-in and says her mother, Jeong-nam, was Hyeon-soo's first love. Hyeon-soo doubts her, so a DNA test is done and shows the two are related.