might read

Yeon-woo had a twin brother who disappeared five years ago. One day, a pocket watch left by his brother returned to his possession. Inside, he found a hidden diary in which was recorded "By the time you hear this, I guess I will be already dead."

I was a chained dog in my past life. I didn't remember my parents and I lived an emotionless life; like a tool. That life ended with my master horrifically killing me. I thought that was the end of my life. But when I opened my eyes again, I was born