I Failed to Escape After Treating the Mastermind

19+ Reverse Harem — I Opened My Eyes as Rebelline Ethellion, the Male Lead’s Younger Sister.
I had absolutely no interest in my brother’s love life.
That is, if only my brother weren’t the tragic male lead who dies near the end of the original story!
‘First, I need to save my brother!’
To do that, I had to be wary of the man who would corrupt my brother with demonic energy.
Chedwin Velharque, the mastermind of the original story.
Rebelline was a 10th-grade Purifier, considered completely useless because she couldn’t purify people.