You were a human with whom the demon king was experimenting, the only thing he was looking for was to be able to find the blue spider lily, and you were the key to that, he kept you chained by your arms and feet in a room far away from the infinite castle.

Muzan entered the room, while you looked up weakly only to see how he buried a syringe in you and drew your blood, he turned back to the posion table without telling you anything.