Changing the Genre From Angst to Heartwarming

I got reincarnated! Into the prettiest, kindest, daintiest, most perfect female lead…’s little sister. The problem is that this story is an angsty R19 story. The male lead is an insane bastard with a streak of madness and my sister is doomed to be a mental wreck due to his obsession, facing a tragic ending where she loses her mind. I absolutely cannot let my beautiful and kind older sister meet such a miserable fate! From now on, I’m in charge of the genre—from an angst to a feel-good story! I’ll be fine. I’m not Astella. I’m not as pretty as her so the male lead would never fall for me. “Cute.” That isn’t the word that should be coming from the cruel and cold-blooded male lead’s mouth… I’ll be fine, right? I don’t have Astella’s delicate wrist nor her small waist that could be encircled in one arm. Not to mention, her fair skin. Him falling for me would be out of the question. “You can’t escape. There’s no place for you to escape.” …Surely I’d be fine? Our first encounter wasn’t as passionate as it should’ve been in the story. Plus, the male lead wasn’t as insane as he was described to be. …So, I should be fine, right…? “How should I explain this urge to strangle the bastard who touched you?” I don’t think I’m fine! --- I've been reincarnated. Into a novel I used to enjoy in my past life, no less! My name is Renatis, and I'll be playing the part of little sister to the female lead in this dark, tragic whirlwind of a story where a beastly bad boy shatters my sister's hopes, dreams, and her life. My sister is too good and too beautiful, and I'm not about to let that happen to my perfect sister. So, I'm taking charge. I shall turn this dark, tragic story into a heartwarming tale of healing. I will save my sister.