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?
but for you to act like this, 
it's not like you, Koyo—
aber warum behandelst du mich so?
pero esto no es propio de…
pero esto no es propio de…
mais c’est pas une raison
pour réagir comme ça !
ma il modo in cui ti comporti
 non è proprio da te.
mas você não é de agir
desse jeito, Koyomi!
но это ведь не повод?..