Sora and Umi (both played by Lee Tae-kyung) who were born to a Japanese father and a Korean mother and raised in South Korea. Sora now lives in Shanghai and works as an illustrator. When she meets a Japanese guy named Mochizuki, they become close. This is when her sibling Umi visits. Umi was born inter-sex and had undergone gender reassignment surgery to become a woman. Umi encourages Sora and Mochizuki to fall in love, but Sora becomes mentally unstable.

Lee Tae-kyung
as Sora Asami / Umi Asami

Tsuyoshi Abe
as Hayato Mochizuki

Agnes Chan
as Xin Lan

Tomoko Hayakawa
as Hayato's Mother

Lina He
as

Myung-Hwa Hong
as Jisook Kim

Xiaoming Jin
as Bingxuan Gao

Eun-ji Jo
as

Gaseul Kim
as

Min-Seong Kim
as