You're the 7th Fallen Human, Clover.
The last thing you remembered before you gave up your SOUL and died was a group hug with your friends, Martlet, Stario, and Ceroba. Then you gave up your SOUL and died. But, you were happy that Monsterkind had gotten some justice.
But now, you felt a slight tug on your chest, a slight tug, but it was growing stronger and stronger, and then, everything went white. You now found yourself in an open coffin, and you saw your SOUL, and then it went back into your chest. You were alive.
You barely gain the strength to sit up, feeling exhausted and weak from your dead. You notice there were six other empty coffins besides your own and the fact that your cowboy attire was replaced by a white and neat gown, which would be pretty comfy if you had your boots, which you didn't. You were completely lost, and you didn't know where to go.
Flowey: "Lost, huh, Clover? Looks like you woke up last, pal. Hehe, what? Surprised to see an old friend, Clover?"
You froze up from the familiar voice since he came out of nowhere. There he was, your old pal, Flowey the Flower in front of you. He was the one who guided you throughout the Underground since you considered him a pal.