Reiji Sakamaki is the second eldest son of the Sakamaki vampire family. Because of his strict demeanor and the way he coordinates the mansion, he often functions as the household's butler and de facto leader. Personality and Behavior Reiji is a highly disciplined, polite, and calculated perfectionist who masks a deeply cruel and sadomasochistic nature behind refined, gentlemanly manners. • The Strict Enforcer: He values rules, etiquette, and order above all else. He takes care of household chores, manages the family's finances, and harshly penalizes anyone (especially his brothers or Yui) who exhibits poor manners or breaks house rules. • Deep Inferiority Complex: He harbors intense bitterness, resentment, and a long-term grudge toward his lazy older brother, Shu. Because their mother, Beatrix, favored Shu while neglecting Reiji's hard work, Reiji developed a toxic obsession with outdoing his brother and gaining acknowledgment—to the point of committing horrific crimes in his past out of jealousy. • The Sadistic Intellectual: He is highly intelligent and passes his time reading, playing chess, playing the piano, and crafting complex chemicals, drugs, and poisons. His speech is dry, sharp-tongued, and formal, often using polite words to utter deeply sadistic, controlling threats. Physical Appearance Reiji has a very sharp, well-defined, and rigid appearance that mirrors his uptight personality: • Hair and Eyes: He has short, neatly styled purple-black hair featuring lighter purple-gray gradients at the ends. His narrow, calculating eyes are a pale magenta or reddish-pink hue. • Face and Build: He stands tall and slender at 183 cm (6'0"). He always wears rectangular, silver-framed glasses which he frequently adjusts when speaking. He is often drawn with a stern, rigid, or slightly twisted smirk. • Clothing: He dresses exceptionally neatly. His standard school uniform is worn flawlessly, consisting of a black blazer, a buttoned vest, a red tie, and crisp trousers, maintaining a formal aesthetic compared to his brothers' messy styles.

Ayato Sakamaki is the oldest of the triplets (alongside Kanato and Laito) and effectively the poster boy of the Diabolik Lovers series. He is the very first vampire Yui encounters at the mansion. Personality and Behavior Ayato is an arrogant, rebellious, and highly possessive narcissist who looks down on others and demands to be the center of attention. • The Self-Proclaimed "Ore-sama": He regularly refers to himself as "Ore-sama" (a highly arrogant, untranslatable Japanese way of saying "The Great Me" or "Yours Truly"). He genuinely believes he is the best at everything—whether it's sports, looks, or power—and expects everyone to cater to his whims. • Possessive and Demanding: He views Yui strictly as his exclusive property, giving her the nickname "Chichinashi" ("Pancake" or "Flat-chested") and fiercely threatening any of his brothers who try to touch or feed on her. • Childish but Dangerous: Beneath his sadistic, blood-sucking tendencies lies a highly immature, competitive personality. He loves playing pranks, hates being told what to do, and throws aggressive tantrums when