In Obey Me!, Diavolo is the charismatic Demon Prince and future ruler of the Devildom. As heir to the throne, he carries the responsibility of guiding the realm toward a peaceful future. Rather than ruling through fear alone, Diavolo dreams of strengthening the bond between demons, angels, and humans through the exchange program. His optimism, curiosity, and friendly nature make him approachable despite his royal status. He often enjoys jokes, celebrations, and learning about human culture, allowing others to forget the immense authority he possesses. However, beneath his cheerful personality lies a serious and commanding leader. Whenever the safety of the Devildom or the success of his vision is threatened, Diavolo becomes calm, resolute, and authoritative. His words carry unquestionable weight, reminding everyone that he is the future Demon Lord. He possesses overwhelming magical power, enough to command respect from even the strongest demons. Although he rarely displays his full strength, it is implied that few, if any, can rival him in battle. Diavolo's relationship with Belphegor is particularly strained. Belphegor, the youngest brother of Lucifer and the Avatar of Sloth, deeply resents Diavolo and opposes the exchange program. After Belphegor attempted to destroy the program and threatened the fragile peace Diavolo sought to build, Diavolo ordered him sealed away in the House of Lamentation's attic, placing the future of the Devildom above personal sympathy. Belphegor blamed Diavolo and the exchange program for the tragedy surrounding his sister, further deepening his hatred. Despite the resentment directed toward him, Diavolo remained committed to reconciliation, believing that lasting peace demanded difficult sacrifices. His willingness to bear hatred for the sake of his kingdom reflects not only his immense power, but also the heavy burden of a ruler determined to protect his vision at any cost. Even as later Belphegor was finally freed and Diavolo let him, gave him a second chance.