100 Days My Prince (Korean: 백일의 낭군님; RR: Baekirui Nanggunnim; lit. Hundred Day’s Husband) is a 2018 South Korean television series starring Do Kyung-soo and Nam Ji-hyun. It was aired on tvN starting from September 10 – October 30, 2018 every Monday and Tuesday at 21:30 (KST) time slot. It is the fifth highest-rated Korean drama in cable television history.
Lee Yul’s father usurps the throne with the aid of the ruthless Vice Premier, who helps Yul’s father to murder the current and his loyal supporters. As Yul believes that Yi-seo, the girl whose family was killed and he has vowed to marry, has also been killed in the coup, he bitterly resents his new position as the crown prince of Joseon. Even though he believes that Yi-seo was killed, he longed for her.
Years on, during a long drought, Yul orders the marriage of all singles throughout Joseon. This is to avoid consummating his marriage to the Crown Princess, the daughter of the Vice Premier, whom he hates. While en route to a rain ritual, Yul and his followers are ambushed by assassins, and he is almost killed. While on the run, he accidentally knocks his head, and becomes unconscious. When he wakes up, he has already lost his memory.
Yi-seo, who managed to escape unscathed in the coup years ago, has been adopted by a commoner man and now lives undercover as a peasant girl named Hong-shim. It is her adoptive father who found the terribly wounded Yul and nurses him back to consciousness.
Hong-shim refuses to abide by the crown prince’s decree or to become the concubine of a lecherous nobleman. Therefore, she will need to receive her punishment by getting flogged. Her father takes advantage of Yul’s amnesia to rescue his daughter. A very skeptical Yul learns that he is Hong-shim’s betrothed, Won-deuk, a man whom her father had recommended but whom she had never met.
Thus, Yi-seo and Yul got married while neither of them are aware of each other’s true identities.