After She Died, I Became the Strongest

My sister and I are both losers and were bullied in our family. I practiced hard and wanted to change my destiny against the will of heaven. My sister was idle all day long. I despised such a sister who didn't understand anything. It wasn't until my father pushed me into the devil's cave that I realized that it was me who didn't understand anything. Short story, misunderstanding, obsession, a bit sadistic