Bokura no Koi wa Shi ni Itaru Yamai no You de

During their childhood, twin brothers Umi and Sora formed a close bond with a young girl named Beniko when she was just four years old. As the years passed, their lives took different directions. Umi eventually moved away, leaving his brother behind. Sora, however, remained deeply connected to Beniko, ultimately confessing his feelings to her with a solemn promise: he intended to propose to her on the day she turned eighteen. Tragedy shattered those hopes when Sora was suddenly killed in a traffic accident, leaving Beniko to grapple with devastating grief. Yet, in the wake of his death, an inexplicable mystery unfolds. Umi unexpectedly reappears before Beniko, but he is no longer the distant twin she once knew. Instead, he looks and behaves exactly like his deceased brother, perfectly mirroring Sora's mannerisms and presence. This eerie transformation leaves Beniko caught between mourning the boy she loved and confronting the unsettling reality of the twin who has taken his place, raising haunting questions about what truly happened after the accident.