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?
So I'm sure that the me in your world 
is waiting for you to return, too.
Darum warte ich in deiner Welt bestimmt
auch darauf, dass du zurückkommst.
Seguro que el yo de tu mundo
también espera que vuelvas.
Seguro que el yo de tu mundo
también espera que vuelvas.
Le moi dans ton monde
Perciò sono sicuro
Portanto, tenho certeza
Поэтому, поверь…
я из твоего мира тоже…