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?
Because of the identity diffusion, 
this person was no longer 0 numerically.
Da eine Identitätsdiffusion stattgefunden hat,
ist sie auch nicht auf null.
Ocurrió la dispersión de la identidad
Ocurrió la dispersión de la identidad
L’identité de la Kazune
de mon monde
A causa della diffusione dell'identità,
Ocorrerá uma dispersão de identidade
Плюс произошло расщепление линии…
Поэтому и эта Кадзунэ не «нулевая».