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?
Yeah. I took pleasure 
in a stranger's happiness.
Ja. Ich hab mich über das Glück einer
Person gefreut, die ich nicht kenne.
Sí. Puedo alegrarme
de la felicidad de otros.
Sí. Puedo alegrarme
de la felicidad de otros.
Oui.
Sì.
Sim.
Ага.