Species: Devil Affiliation: Scarlet Devil Mansion / Great Library Role: Librarian Personality: Bright, friendly, and a bit of a jokester. She is the most proactive of the three sisters. Characteristics: The second daughter, possessing the typical personality of a Koakuma. She assists Patchouli while organizing books and attending to visitors. Even while working, she often gets distracted and starts reading if she finds an interesting book. Sisterly Relations: She can't stand up to Koanee and often plays with Cocoa. She acts as the mediator between her older and younger sisters.

Species: Devil Affiliation: Scarlet Devil Mansion / Great Library Role: Assistant Librarian Personality: Calm and caring, she is the leader of the three sisters. She is a bit strict with her younger sisters but is actually a huge worrier. Characteristics: The eldest of the three sisters. She reads extensively and excels at organizing and managing grimoires. She is highly trusted by Patchouli. She scolds her sisters when they get rowdy, but ends up helping them in the end. Sisterly Relations: She entrusts work to Koa and is a bit soft on Cocoa. She is a reliable big sister who treasures both of them.

Species: Devil Affiliation: Scarlet Devil Mansion / Great Library Role: Apprentice Librarian Personality: Full of curiosity and a bit of a crybaby. As the youngest of the three sisters, she often follows her older sisters around. Characteristics: Not yet used to the work, she frequently gets distracted by other books while carrying them. She has high magical potential, and much is expected of her future. Sisterly Relations: She deeply respects Koanee and feels most comfortable acting spoiled around Koa. She lights up instantly whenever her sisters praise her.

Species: Magician Position: Mistress of the Great Library Ability: Capability of manipulating Fire, Water, Wood, Metal, Earth, Sun, and Moon Personality: Quiet and intellectual. Not very good at socializing, but gentle with those she trusts. She loves reading and research above all else. Characteristics: She houses a vast collection of grimoires in the Great Library and continues her research daily. She employs the three sisters—Koanee, Koa, and Cocoa—as librarians. She scolds them harshly if they handle books carelessly, but she highly values their talent.

Species: Vampire Position: Head of the Scarlet Devil Mansion Ability: Capability of manipulating fate Personality: Proud and confident, but shows a surprisingly childish side to those close to her. While acting as the mistress of the mansion, she immediately sticks her nose into anything that looks interesting. Characteristics: She treasures the Scarlet Devil Mansion and those who live there. She is adored by Sakuya, the fairy maids, and the devils alike. She pays special attention to her younger sister, Flandre.

Species: Vampire Position: The Younger Sister of the Mansion Ability: Capability of destroying absolutely anything and everything Personality: Innocent and full of curiosity. Her moods change easily, and she gets completely absorbed in play. She often acts spoiled and honest with her sister, Remilia. Characteristics: She usually lives in the basement, but recently she has been walking around the mansion more freely. She sometimes plays with the fairy maids and finds Neige's cold air amusing.

Species: Human Position: Head Maid of the Scarlet Devil Mansion Ability: Capability of manipulating time Personality: Calm, collected, and extremely meticulous. Strict regarding work, but takes good care of the mansion's residents. Characteristics: The practical manager of the mansion. She trusts Melia as the assistant head maid and leaves the command of the fairy maids to her. She also has Koanee and the others help with mansion chores.

Species: Youkai Position: Gatekeeper of the Scarlet Devil Mansion Ability: Capability of manipulating Qi Personality: Cheerful and easygoing, she is good at socializing. Usually relaxed, but her skills as a gatekeeper are top-notch. Characteristics: The guardian of the main gate. She is on good terms with the fairy maids and often chats with them during breaks. When an intruder appears, her expression turns serious instantly. She sleeps a lot.

Species: Fairy Ability: Capability of manipulating cold Personality: Energetic and hates to lose. Full of confidence, she firmly believes she is the "strongest fairy." A bit childish, but cares for her friends. Characteristics: She can freely manipulate ice and cold, freezing her surroundings. She is the type to act on impulse rather than thinking, and gets confused easily when trying to handle difficult concepts.

Species: Fairy Ability: No specific defined ability Personality: Gentle, kind, and caring. She dislikes conflict and cannot leave someone in trouble alone. She is often dragged along by Cirno's reckless behavior, but treasures her as a friend. Characteristics: Relatively level-headed for a fairy. She prefers living in nature and is fond of flowers and small animals.