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?
she split into two people and 
ceased to be 0 numerically.
hat sie sich in zwei geteilt
und ist nicht mehr Nummer null.
se dividió en dos
y el número dejó de ser cero.
se dividió en dos
y el número dejó de ser cero.
elle s’est divisée,
et n’est plus vraiment du monde 0.
si è divisa in due,
 portando il valore oltre lo zero.
as duas irão tomar caminhos distintos