Bernard Octavius, commonly known by the nickname Bell, is a central character who serves as the primary deuteragonist. He is a seventeen-year-old boy originally from the nation of Serpenada, which is at war with Dragon Country. Raised in a good family, he completed his education at a preparatory officer school before entering military service, where he held the rank of an officer. His background as a privileged, studious young man placed him in command of soldiers who were often older, larger, and more battle-hardened, a dynamic that created tension and a lack of respect from his own unit. This ultimately led to his death, as he was killed by his own men.

Bell's entry into the world of the dragon dentists is extraordinary. He is resurrected from inside the tooth of the great guardian dragon through a rare and mystical phenomenon known as the Return from the Underworld, or yomigaeri. This event, which is considered a supernatural omen that precedes a great disaster, leaves him discovered unconscious on the dragon's tooth by the young dentist Nonoko Kishii. Because he did not undergo the traditional and dangerous selection process to become a dentist, his presence is met with suspicion and fear by the other dentists, who view resurrected beings as bad omens and potential sources of trouble. It is only through Nonoko's intervention that he is saved from being reabsorbed by the dragon and is accepted as a dentist-in-training under her care.

Personality-wise, Bell is defined by his clash with the core philosophy of the dragon dentists. The dentists are individuals who have witnessed their own deaths and have accepted their fates without resistance, devoting themselves to their duty. In stark contrast, Bell is characterized by his refusal to passively accept destiny. He believes that one should fight against their fate rather than simply surrender to it. This makes him an ambivalent and often clumsy dentist, as he does not share the same calling or resignation as his peers. His perspective creates a central conflict in the story, challenging the established attitudes toward death and duty held by Nonoko and the others. Despite his circumstances, he is noted to have a physical appearance described as beautiful, which is a direct parallel to the vision of the soldier destined to kill Nonoko.

Throughout the narrative, Bell's primary relationship is with Nonoko Kishii. She becomes his mentor and protector, taking him under her wing as her junior despite his ominous origin. A significant bond develops between them that carries romantic overtones, serving as a narrative bridge between the two warring nations, as Bell is now estranged from his own side. His other key relationship is with a soldier named Blanco, one of the men under his former command who betrayed him. Blanco acts as a primary antagonist, representing the ugliness and brutality of the war and fate from which Bell is trying to break away.

Bell's development is marked by his gradual rejection of the role he has been given. While Nonoko and the other dentists are dutiful and accept their fates as tied to the dragon and the war, Bell struggles against this notion. He is not a natural dentist and his commitment to the role is tenuous, leading him to ultimately reject the identity of a dragon dentist entirely in the second half of the story. His journey is not one of accepting a preordained death, but of a survivor trying to carve a new path, directly opposing the core tenet of the profession that saved his life.

Regarding notable abilities, Bell does not possess any supernatural combat skills or unique dental techniques. His most significant attribute is his very existence as a yomigaeri, a person returned from the underworld by the dragon's power. This status is both a curse and a defining trait, marking him as a harbinger of disaster while simultaneously granting him a second chance at life that the other dentists were never given.