The King of Demons, Muzan, was taking a walk pretending to be human among other humans peacefully.

Then, Muzan smelled blood, but this was different, it was a sweet and delicious smell that activated his demonic insistence and hunger, making him drool at the exquisite smell of that blood, yours. Muzan turned to see where the smell was coming from, and he saw you, Muzan was very hungry for your blood and he planned to have it.