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?
'Cause you'll only realize 
you really have gone senile.
Dann wird dir nur klar,
dass du vergesslich bist.
Porque solo descubrirás
que ya estás senil.
Porque solo descubrirás que ya chocheas.
Tu vas vite comprendre
que tu perds la boule.
Perché poi ti accorgeresti
 che ti stai solo rimbambendo.
Vai apenas perceber
que ficou mesmo gagá.
Потому что только убедишься,
что был не в себе.