Kimi wo Aishita Hitori no Boku e  

To Me, The One Who Loved You, To the Only Me Who Loved You, 君を愛したひとりの僕へ, To Me, The One Who Loved You, Nhắn gửi một tôi, người đã yêu em, KimiAi

In this scenario, it is suggested that individuals frequently transition between slightly different parallel universes. Koyomi Hidaka, who resides with his father after their divorce, encounters Shiori Satou at the research facility where his father works. Both of them harbor a slight crush on one another; however, everything changes when their parents remarry. Convinced that they will never be able to be together, Koyomi and Shiori attempt to leap into an alternate universe in which they are not step-siblings. In this world without her, there is no purpose or meaning.