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?
Like binary stars, they could influence 
each other and remain equidistant...
Ob sie sich wohl wie Doppelsterne
in gewisser Distanz beeinflussen
¿Avanzarán en la misma dirección
influyéndose,
¿Avanzarán en la misma dirección
influyéndose,
Sauf si, comme des étoiles binaires,
ils avancent conjointement
Si manterrebbero equidistanti,
 come una stella binaria,
Podem ser como estrelas binárias, mantendo
distância enquanto causam efeito uma para a outra,
Подобно двойной звезде, они равноудалённо
продолжат двигаться в одном направлении?