I Just Want to Lie Flat, but the System Wants Me to Win Over the Eerie King

I died naturally in my previous life, then woke up having transmigrated into another world as a baby. My father was the richest man in the county, and my mother was a renowned physician known far and wide. I planned to coast on my parents’ wealth and lie flat for the rest of my life, but the System informed me that if I didn't kill or win over the Ghost King, I wouldn't live past eighteen. What else is there to say? I have to kill the Ghost King to uphold my way of lying flat!!!!