To Me, The One Who Loved You

Koyomi Hidaka, who lives with his father after his parents' divorce, works at a research institute where his father is employed. It's there that he meets Shiori Satou, with whom he shares a mutual crush. However, their relationship is complicated by the fact that their parents eventually remarry, making them step-siblings. This leads Koyomi and Shiori to attempt to jump into a parallel world where they wouldn't be related.