“Narye, if you become a Yin, will you be my Yin?”
“Hyung-nim, if I’m a Yang, will you hate me?”

Prince Lee SeoYo was sure he would become a Yang.
However, on his 13th birthday, when he is revealed to be an ordinary person, he is kicked out of the palace and stripped of his title and everything he has.

One day, after Lee SeoYo has left behind his life of splendor in the royal palace and his past, Narye, who he had said he would take as a companion even if he was a Yang, appears before him. Even though he had nothing.

“Dream of me. Think of me. Only go into heat for me.”

In the distant future, Yoon SeoYo is born with the memories of his past life and Lee SeoYo. Kwon Chaheon, who has a face that resembles Narye’s, but a completely different personality, appears before him. Yoon SeoYo, who initially tries to push him away because of the terrible memories from his past life, gradually opens his heart to his kindness.

“Yoon SeoYo, you don’t have any friends.”
“Don’t I?”
“Then I’ll be your only one, your friend.”