I really love seeing Jisuh and Sun-yool together but the very fact that they can't be is I definitely know.
To be honest, I hated Heejae for what his done but I know he is making up for those bad things.
But if Sun-yool will be gone in the story after this, i guess the title and cover of the manhwa will be a little off.
http://www.mangago.zone/read-manga/kirei_na_onii_san_ni_horeraremashita/uu/kirei_na_onii_san_ni_horeraremashita-chapter-1/3/