SonWu SoeYin is one of the ministers of GaGook. He is also an agent of the Crimson Moon who provides intel from the palace.
He has gray-brown hair and eyes of the same color.
As a young man during the reign of King JinHyul, SonWu SoeYin was engaged to BeckHwa Sah. When BeckHwa's father was executed for treason, SonWu pleaded with his father to have BeckHwa released from prison, but instead his father forced him to break his engagement. As BeckHwa was being led out of the city in a caged wagon, SonWu appeared in the rock-throwing crowd, calling her name. She responded by tossing away her engagement ring, which became crushed under the wagon's wheel. SonWu dropped to his knees in despair.
Several years later, the son of a minister brought SonWu with him to the JuWah District and teased him for clinging to the memory of a woman who died in exile. But when he recognizes the arriving courtesan, who introduces herself as "Crescent Blossom", their old feelings returned as their tears began to fall.
At JinHee Palace, SonWu SoeYin is one of the ministers in attendance of a meeting with King JinWon, who daydreams about Nabi while the ministers discuss refugee aid and army budgets.
During a secret meeting at YuHyang Ru with Nabi, Juk Lee, and YoungHwa Wol, SonWu SoeYun provides a map of Councillor Jagyum Yu's home as well as information about the Covenant—that it had been recently moved from the Queen's Quarters to the Councillor's residence. An inspector who was tracking its movement disappeared, and palace security has doubled. YoungHwa suspects that this is a trap, but both Nabi and Juk Lee are determined to steal it, anyway. SonWu SoeYin then places a scroll on the table upon which everything that recently passed through the Councillor's home was recorded. Once the two younger men decide to steal the Covenant that night and leave to prepare, SonWu SoeYin notes that they have grown up to be very stubborn. He recalls the night of the palace fire when he gambled by sending the boys to YoungHwa, especially considering how her own parents died. He expresses his gratitude for her help all those years ago. As he squeezes her hand, he makes a promise to himself that he will always protect YoungHwa and her daughter SolHwa.