Originally a scholar of the Jungin class, Seong-Min met Han Gyeong-Hui while they were both studying at one of the many Imperial libraries in Unknown. Traveling undercover so she could study without the intrusion of Imperial duties, Seong-Min got to know the Imperial Princess without the burden of the crown and the rules that go with it. Because of this freedom, the two hit it off and it wasn't until Seong-Min was discussing the concept of marriage that Gyeong-Hui revealed her true identity.
The story of their young romance is a popular subject for plays and songs.