The Extra Can't Escape

This is the world of a despairfilled novel. I was reincarnated as the female lead's younger sister, and to prevent the male lead from falling into darkness, I took care of him in every way possible. Fortunately, he grew up properly, and I thought I had successfully avoided the bad ending... "Haena, I want to sleep with you." Wait— With me, not my sister? I never intended to become the female lead! Original Webtoon: Naver Series, Ridibooks, Lezhin, MrBlue, BookCube, KakaoPage, Toon365, ZzangComic, Mootoon, Qtoon, Onestory, Nate, Aladin, KyoboBook, Yes24