Set during the Joseon Dynasty ,Chunofollows the story of Lee Dae Gil, Song Tae Ha and Kim Hye Won.
Lee Dae Gil is a man from a noble family, whose life is ruined by Keun Nom (큰놈이/Big One), who is a slave owned by Dae Gil's family. He burns down Dae Gil's house when his sister Un Nyun is locked in a shed and left to die by dehydration because she and Dae Gil are in love. When he sets the house on fire he uses a sickle to slash Dae Gil's face. The house collapses shortly after, and Keun Nom and Un Nyun think Dae Gil is killed.
Keun Nom runs away with Un Nyun and eventually accumulates enough wealth to buy Jokbo of a noble family. Assuming the identity of the yangban Kim family, he then changes his name to Kim Seong Hwan and his sister Un Nyun's name to Kim Hye Won. Driven by his desire for revenge as well as his obsession/love with Un Nyun, Dae Gil endures ten harsh years on the street and makes his name as a slave hunter. Dae Gil carries a sketch of Un Nyun at all times and searches for her wherever he goes.
Song Tae Ha is a military general who has spent years serving the crown prince in China, who has been held as a hostage after Joseon lost the war with the Qing Dynasty. Upon their release to Joseon, they find themselves embroiled in an even bigger political turmoil. The crown prince dies under suspicious circumstances shortly after returning to Joseon, the crown princess and two of his three young sons are also killed, and the youngest son is exiled on Jeju island. Tae Ha is framed for stealing military ration, and is demoted to a slave along with his loyal subordinates.
When Tae Ha learns that the exiled youngest son of the late prince, who he believes to be the only rightful heir to the crown, is in danger, he is determined to protect him and have him declared the new crown prince. He escapes forced labor and sets off his journey to Jeju island. Along the way, Tae Ha comes across Hye Won/Un Nyun, who is on the run from an arranged marriage to a powerful noble, and saves her from danger. Dae Gil is hired to capture Tae Ha and chases after him, who, unbeknownst to Dae Gil, is now traveling, and starting a romantic relationship with the woman he has been obsessively searching for ten years.