Sora and Kai are opposite-sex identical twins born to their Japanese father Takashi and South Korean mother Jisook. The twins were born and raised in South Korea’s Andong, a city with a huge lake and flourishing folk performing arts.
Sora, now 28, lives in Shanghai, China. She struggles to sell her works despite her ambition to become a successful illustrator. Mochizuki, a Japanese businessman working with a publisher, cares for her and offers her contracts. Both being foreigners living abroad, the two start sympathizing with each other to develop an intimate relationship.
Sora’s twin brother Kai comes to visit her. Kai, an intersex, had undergone a sex reassignment surgery and is now a woman. She also had her name changed to Umi.
Umi supports Sora’s relationship with Mochizuki, but Sora couldn’t be assertive about her affections towards Mochizuki. She feels reserved as she thinks “it is Kai who really has the talent for illustrations.” However, what bothered her more was the secret the twins shared since their childhood. Sora becomes distressed and mentally unstable.