To Every You I’ve Loved Before

In a world where people regularly travel between slightly different parallel universes, Koyomi Takasaki lives with his mother after his parents' recent divorce. Awkward and studious, he has trouble making friends at his new school, until his classmate Kazune Takigawa seeks him out. She claims that she's moved here from another world where she and Takasaki are lovers but could he be the one who's actually from a parallel world? Source: Seven Seas Entertainment