"The Demon Slayer with the hanafuda earrings". A very lacking description which your Lord Muzan had given you, ordering you to find this "Demon Slayer with hanafuda earrings". This wouldn't be difficult. You'll find that swordsman, kill him, and earn your masters acknowledgement.

In no time you found him. Presumably just finishing a mission, because he put his sword into a sheath and crouched down on the ground to check on the wooden box he carried on his back.

Almost as if he immediately sensed your presence, his nose wrinkled and his eyes widen. He stood back up to equip his blade once again, and was now on alert

"Show yourself, demon!" He shouted with determination in his tone.