France, 2039. One night, a group of activists pursued by the state vanish without a trace. Julia Bombarth is one of them. When she awakens, she finds herself trapped in an entirely unfamiliar world PLANET B.
Yujeong, who works as a night shift nurse at a general hospital's cardiology department, is now told that her 12th-grade younger sister, Kijeong, has been arrested by the police as a suspect in an infant abandonment case. Only then does Yujeong start to make desperate efforts to rescue her sister.