After decades, Tae-soo reunites with his twin sister, Tae-hee. However, Tae-soo is unrecognizable and now goes by the name Kit. At first, Tae-hee doesn't believe a word he says, claiming there is no way he is her deceased twin, until he discloses secrets from their shared past.
Tae-hee introduces Kit to KSH House-a small business that deals in estate sales and antiques-where he meets businessman Sameer Khan and the charismatic Jong-hyun Park. As he settles in with the members of KSH House, Kit's budding friendship with Jong develops into a romance. Fate tests their relationship when the hidden past of Kit and Tae-hee is exposed, linking them to beings of energy called threlphax. Meanwhile, a threat emerges that takes the life of a friend and places the future of KSH House members and threlphax in jeopardy.