To Me, The One Who Loved You

After his parents’ divorce, seven-year-old Koyomi Hidaka chooses to live with his father, a researcher at the Japanese Institute of Virtual Science studying the existence of parallel worlds. Through his father’s work, Koyomi meets Shiori Satou, the child of another divorced scientist, and the two quickly become close. Their friendship carries them through childhood, deepening into a bond strong enough for them to dream of marrying someday.

Those plans are shaken when their parents decide to marry each other, turning Koyomi and Shiori into step-siblings. Unable to accept the life suddenly laid out for them, they turn to the parallel-world research surrounding them and flee to another world to begin again—only to discover consequences that threaten the future they were trying to protect.