Read manga: Bokura no Koi wa Shi ni Itaru Yamai no You de

manga
Summary:

As children, Umi became acquainted with a four-year old Beniko. Meanwhile, Sora confessed to Beniko that he'll propose to her when she turns 18. Unfortunately, he died in a traffic accident. He then appears before Beniko, Umi, Sora's younger twin, with the voice, figure and everything else like him. Beniko, had to confront the twisted love and affection given to her by Umi, instead of Sora from...?!