Tokyo, at present.
NASA announces the discovery of a new planet in the solar system, Emanon, where life might exist. The shocking news spread throughout the world, then a fad of the new planet emerges. Despite people’s enthusiasm, abnormal weather events occur frequently.
Working part-time at a travel agency, Mika (Azusa Inamura) is doing her Master’s degree in theoretical physics. She hasn’t been able to get over Teru, her boyfriend who disappeared five years ago. Mika looks like an ordinary graduate student. As a matter of fact, she spends every day talking to Teru in her delusions while hunting men using a dating app to distract herself from the loneliness. Seeing Mika like this, her best friend, Shige (Seicho Yoshino), a gay man, and Takayama (Mutsumi Sato), her senior at her graduate school laboratory, are concerned for her.
One day, Mika suddenly experiences déjà vu and meets a version of herself. Both Mikas are startled to see each other, and they fall into a perplexing situation. Mika goes to see Bird (Leo Imamura), Teru’s best friend, and she meets a third Mika there. It is revealed that three of them exist in the different world lines. Bird says that Emanon might have caused the parallel world to intertwine.
Three Mikas: one lives in a world where Teru disappeared; the second one lives in a world where she meets Teru and their romance begins; the third one lives in a world where Teru has already passed away. The worlds where the three of them live start to loop. Due to Emanon, some kind of errors occur in space and time.