Shiba Miyuki remembers the events from three years ago. At the time, Tatsuya had already been assigned to be her guardian, but he still hadn’t become the most important person in her life. This incomprehensible older brother—always with an unruffled face—behaved impeccably, yet somehow constantly worried and irritated Miyuki. And yet it was then, three years ago, that happened that fateful moment on the border between life and death, completely changing everything…