Wang So, a Goryeo prince, was born with the name, "Shine". Shin Yul is a woman hailing from the Balhae kingdom and believed to have the powers of an oracle. A prince who suffered vile remarks because of a cursed prophecy finds himself attracted to a former princess from a fallen kingdom who faces death because of her fate to become the light of another kingdom. Their love is at a point of either shining or flaming out.
Wang Soe gets exiled to Geumgang Mountain by Wang Gun due to his cursed fate. Years after, Wang Gun summons Soe back to the palace. Then they get attacked by assassins.
One the night that Wang Soe and Shin Yule have a fake marriage, the Star of War and Star of Alioth meet. When Jimong saw the two stars, he becomes sure that Princess Yeowon is the right match for Soe.
5 years after, Cheonghae guild opens business in Byeokrando. Shin Yule thoroughly prepares the goods she will trade with the Royals during the Buddhist Ceremony. Princess Yeowon meets Yule for the first time and is intrigued by her wisdom.
Princess Yeowon joins hands with Wang Siklyeom in order to make Wang Wook the king of Koryo. Wang Siklyeom tells Princess Yeowon to find a way to take the king down.
Wang Soe loses his jade ornament, given by Shin Yule when he goes into Cheonghae Guild's storage room to find out who has Kim Jongshik's back.
Wang Soe is to work at Cheonghae Guild for 5 days. He talks about the order of the world with Shin Yule and realizes that he wants to make her his.
Wang Soe and Shin Yule sneak into the library of the Royal Palace. Yule gets excited about all the rare books that she finds. Meanwhile, Soe secretly goes to see Jeongjong, his brother.
Wang Soe and the Warriors in Black encounters Wang Siklyeom's assassins while tracking down Hong Gyui. Soe realizes that one of the assassins was the one that tried to kill Wang Gun 5 years ago.
Princess Yeowon warns Shin Yule not to be close to Wang Soe and leaves.
Shin Yule finds out that Soe Soe was Prince Soe, who arrives late for the Battle Competition of the Princes. Soon after, people from Cheonghae Guild find out too.
Wang Soe asks why Wang Wook didn't tell him that Kaebong was Shin Yule, a lady. Wook answers that it's because he loves her. The tension between the two rises.
Wang Soe can't take his eyes off of Shin Yule, who is finally presented as a lady. They enjoy their time together, walking around Gaegyeong with their respective attires.
The Queen Dowager summons Wang Soe to Princess Yeowon's room. Shin Yule throws a festival at the guild to hide her confusion.
Wang Soe orders the Warriors in Black to focus on finding the provider of the white poisonous plant. Meanwhile, Princess Yeowon tries to get her hands on the Cheongdong mirror by threatening Cheongok, one of the Warriors in Black.
Shin Yule demand Princess Yeowon to never speak of the marriage in Kaifeng and to give her the antidote. In return, Yule will also never tell Wang Soe that she's the one that poisoned Jeongjong.
Princess Yeowon orders Saewon to kidnap Shin Yule and threatens her that she will bring down Cheonghae Guild.
Wang Wook puts Cheonghae Guild in danger by testifying for a false accusation in order to keep Shin Yule safe.
Wang Soe finds the Cheongdong mirror pieces in Wang Siklyeom's secret chamber. Princess Yeowon teams up with Wang Soe to bring down Wang Siklyeom.
With the help of Wang Soe, Jeongjong tries to prove that Wang Siklyeom assassinated the late King Taejo, but Wang Siklyeom fights back by bringing up the Warriors in Black.
Shin Yule becomes dangerously sick in the prison and Wang Soe doesn't know what to do. Wang Wook shows up to save Shin Yule and plots to save them from the interrogation with Princess Yeowon.
Wang Wook prepares the royal marriage with Shin Yule. Meanwhile, Shin Yule acts and talks as if she is saying goodbye, handing over her work and strategies to run a business.
Wang Siklyeom sends an assassin to kill Shin Yule. Wang Wook, who protected Yule from the assassin, fakes her death in order to keep her safe from Siklyeom.
Seeing his people get mistreated, Wang Soe enrages and fights Wang Siklyeom's private soldiers. The people recognize Wang Soe and help him escape. Meanwhile, Shin Yule's cold poison gets worse and worse.
Jeongjong decides to abdicate his throne to Wang Soe, but he refuses. He then takes the Warriors in Black and go to Cheonghae Village to protect them from Wang Siklyeom as he marches to destroy the village.