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?
Her world had split, 
so when she Shifted back,
Beim Sprung in diese gespaltene Welt
Al volver aquí tras una división,
Al volver aquí tras una división,
En revenant
où la scission s’est produite,
Quando è arrivata in questo mondo, 
dove è avvenuta la ramificazione,
Se a ramificação ocorre e é feita
a mudança paralela para cá,
Она «разделилась» на две мнимости,
когда сместилась к нам после разветвления.