Read manhwa I’m the Master of this Life / 이번 생은 내가 주인입니다
The guardian stone of the family appeared to me. To me, the illegitimate child, not my half-sister who is the enemy. Since then, the treatment of me has changed. It really felt like they were part of their family. However, as he died, he realized that it was all an illusion at the hands of his fiancée. That everything he did for me was a scheme by my half-sister to take the guardian stone.

I decided to accept the devilishly sweet offer. This time, I will definitely get the guardian stone and become the head of the household. I will give you back as much or more than what you suffered. Until then, no one will believe. But…
“From now on, no matter what happens, you must never stop and run.”
The image of him trying to save me, his eyes running in despair, couldn’t be erased from my mind. The fiance I loved is looking at me as I am dying, but why are you running to me with those eyes, who you thought was her sister’s person… … . wanted to know what your sincerity is.
https://teenmanhua.com/manga/im-the-master-of-this-life