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?
you Shifted from world 0, where you left
 the item there, to world 1, where you didn't,
dann ist man von der Welt null in die Welt eins,
in der man nicht aufgeräumt hat, gesprungen
viajas del cero, donde lo guardaste,
al uno, donde no,
viajas del cero, donde lo guardaste,
al uno, donde no,
puis elle a été transférée
dans le monde 1 où elle ne l’était pas,
da quello, dove avevamo riposto l'oggetto,
Мир, в котором не нашли свою вещь,
в свою очередь, — «первый».