In the Kowloon Castle full of nostalgia, real estate agents Ju Lai Reiko and Kudo Ichima shuttled through the mottled old streets and alleys together.As time goes by day and night, Reiko's feelings for Yishi quietly grew, as if every brick and tile in this old city witnessed her gradually awakening in her heart. However, an accidental discovery teared the gentle calm apart - Reiko found a yellowed photo in a book, where his ex-fiancee stood beside him.At that moment, her breathing stopped.The woman's face was exactly the same as herself. Shock, doubt, and anxiety were intertwined into a chill, quietly climbing into Reiko's heart.She began to examine her past, but found that the memory was as blurred as it was covered by thick fog.Who is she?Why did you come here?Why are those clips about the past blank? In this secret city, a story about identity, memory and love is quietly beginning...