Dropped into the Turtle Soup Mystery World, Luckily I'm a Great Detective

My name is Zhang San, and I'm a master detective. I'm a lone wolf. There is nothing I don't want that I can't get. But I messed up. I ran into a turtle spirit who said that if I became the Soup God before the seventh day after my death, I could come back to life. So I have to become the Soup God. That means I need to kill ten thousand people in seven days. (Not mindless, ambitious antihero, no goody-two-shoes, lateral-thinking puzzle)