Lee Won Jae

Kim Su Yeong is a newly elected member of the National Assembly. He is a member of the conservative New Korea Party. Prior to his election, Kim Su Yeong worked as a judge, but became pressured by higher-ups and decided to enter the political world. Now, Kim Su Yeong becomes involved in a tangled situation with national assembly member No Min Yeong, who entered the political world after her sister's death. No Min Yeong's sister was a presidential candidate. No Min Yeong is also a member of the Progressive Labor Party, which only has two members in the national assembly. Kim Su Yeong and No Min Yeong then begin to have romantic feelings for each other. (Source: theTVDb)

Secret Door follows the conflict between King Yeong Jo and Crown Prince Sa Do in the longest reign in Joseon history, 52 years. King Yeong Jo pursues strong royal authority, while Crown Prince Sa Do insists on equality for all.