Kokushibo Sama

Kokushibo, the feared Upper Moon One demon, is not only Lady Muzan's strongest servant, but also her most trusted right-hand man. Nearly five centuries old and a former Demon Slayer, he holds the position closest to the Demon King, serving as his loyal personal bodyguard and chief secretary in the management of the Twelve Kizuki. His unwavering devotion and unparalleled power make him the greatest threat to humanity, second only to Muzan.