Alright so I was totally wishing for the long hair guy to be the ml but unfortunately his not. It’s the crown prince and the real villain is actually “Siel”.
For starters yes, erquanna is the older sister of eri. It’s weird but bear with me. The youngster sister is actually in the demon realm and they do reunite for a brief moment. Erquanna soul is in her younger sisters body. The only reason why she looks different compared to when she was a child is because one of her kidnappers gave her a potion that changed her hair, eyes and body. She also lost her memory.
Siel is the main villain because he constructed everything that happened to erquanna thus far, apparently there’s a demon residing in him, named Astar Amon. His so obsessed with erquanna that he planed her memory loss and the crown princes because he has the ability to manipulate memories or minds. But yeah that my brief explanation. So disappointed that the ml isn’t the long haired guy, but he does betray the fl! Very unfortunate.
For more insight go here: https://www.novelupdatesforum.com/threads/villainess-resurrection-24-hours-%EC%95%85%EB%85%80-%EB%B6%80%ED%99%9C-24%EC%8B%9C.174325/page-2