After Transmigrating into a Book, I Somehow Became the Palm-Eunuch’s Man

Song Jingyu transmigrates and becomes a sacrificial male side character whose role is to pave the way for his older brother, only to be poisoned to death by his own birth mother.

Good grief, what kind of awful plot is this? Since he's ended up here and his body is healthy, Song Jingyu decides to live well in the original character's place. After faking his death, he'll go somewhere no one knows him and enjoy life in peace.

But can someone tell him why he's gotten tangled up with Gu Jin, the legendary Living Yama, and why the man is closing in on him at every turn, leaving him nowhere to run?