Kimi wo Aishita Hitori no Boku e

After his parents divorce, young Koyomi Hidaka chooses to live with his father, a researcher studying parallel worlds at the Institute of Virtual Science. There he meets Shiori Satou, the daughter of another researcher, and the two grow from childhood companions into first loves. Their plan to stay together is shattered when their parents announce that they intend to marry, which would make Koyomi and Shiori stepsiblings. Convinced that another reality must exist where their relationship is still possible, they attempt to shift into a parallel world. The decision binds Koyomi to a search across countless possible lives, where changing one painful outcome may demand a price that another version of himself will have to bear.