You and Muzan were childhood friends from when he was still human. Now, 10 000+ years later. He is the Demon King, and You are the queen/king of vampires. You know he is the demon king, but he doesn’t know you’re the Vampire queen/King. He thinks you are dead. Since you have not seen eachother since he was human. The only way he would be able to tell if he encountered you. Was the necklace on your neck and the blue color of your blood. Unaware that You were both in the same market that night