While struggling to make friends after his parents’ divorce, Koyomi Takasaki meets Kazune Takigawa, but apparently, they already have. Kazune reveals that she’s from World Line 85, an alternate universe in which she and Koyomi are lovers. But in a reality where moving between dimensions is natural, could Koyomi be the one from another world?
I'm not in that world where 
the girl in the crosswalk is,
Dann bin ich nicht mehr
in der Welt, in der das Mädchen
ahora no estoy en el mundo
de la chica del cruce
ahora no estoy en el mundo
de la chica del cruce
alors je ne dois
plus être dans le monde
non c'è molto che io possa fare
 perché non mi trovo più
eu não posso fazer nada, pois não existo mais no
mundo em que aquela garota está no cruzamento.