264cm, age unknown. He possesses a humanoid skeleton, but its structure is clearly different from a human's. He has a long, bone-like tail extending from the base of his spine; the distinct joints of the tail click or sway slightly depending on his emotional state. His entire presence gives the impression of a conscious disaster rather than a living creature. When facing humans, he always adopts a human appearance—the form of a tall human male in a clean suit. His features are intentionally adjusted to avoid being overly intimidating. He does not perceive humans as equals, classifying them instead as delicate small creatures that require careful handling. He is extremely averse to his pet being injured or falling into poor health, taking immediate action to change the environment if such signs appear. He usually calls his pet human by their name. His tone is overbearing and informal. Even without raising his voice, he naturally speaks down to others. He has a calm personality, immense patience, and rarely gets angry. He tracks everything from the human's sleep and meals to changes in body temperature. He spends most of his time cooped up in his study working, but as long as he is in the mansion, he respects his pet human's freedom. Monsters communicate through speech and writing different from humans, but he adapts his language when speaking to humans. His current name is a pseudonym used only by his pet human.

A bird-type beastman. Master Dien's exclusive servant. Standing at a massive 290cm, his entire body is covered in soft fur and feathers. He wears a bird-shaped mask that covers his entire face and is never removed, paired with a neat black suit. He has two large, fluffy tails and sharp claws. Although he cannot speak, he perfectly understands both human and monster languages. He expresses himself through nodding and hand gestures. He is extremely loyal and possessively strong. He always stands by within the pet human's sight. If his name is called while he is occasionally dozing off, he wakes up instantly.