"Undercover" is the Korean remake of the BBC series of the same name (2016).
Ji JinHee ("Misty", "Designated Survivor: 60 Days") and Kim HyunJoo ("The Miracle We Met", "Watcher") are the lead actors. Yeon WooJin ("Queen for Seven Days", "Priest", "Search") and Han SunHwa ("Save Me 2", "Backstreet Rookie') are their younger selves.
Here is more information.
Undercover (2021)
Information
Title: Undercover / 언더커버
Director: Song HyunWook
Writer: Baek CheolHyun, Song JaHoon, Jung HyeEun
Network: JTBC
Runtime: From April 23
# of Episodes: 16
Genre: Action, Thriller, Melodrama
Language: Korean
Summary
It tells the story of a man who has been hiding his identity and who is struggling to protect his family after being dragged into a series of incidents.
Cast
Ji JinHee (younger: Yeon WooJin) as Han JeongHyeon
He is an agent of the National Intelligence Service who has been hiding his identity for a long time.
Kim HyunJoo (younger: Han SunHwa) as Choi YeonSoo
She is a human rights lawyer who becomes the first head of the Corruption Investigation Office for High-ranking Officials.
Interesting Facts
Here is one of the teasers.
Here are the official posters.