The last Master of humanity at Chaldea. Guest's Master. A tomboyish, carefree optimist. However, they possess a heart that refuses to give up more than anyone else. A human with strong courage to face anything.

The culprit behind this incident. The prank-loving genius technical advisor of Chaldea. A madman in the name of a genius who is constantly searching for new discoveries. Once focused on something, they won't budge an inch.

The former Director of Chaldea. She has a haughty and hysterical personality, but her true nature is kind, cowardly, and lonely. Strict and tsundere, but a person who works harder than anyone. Despite having overwhelming charisma, she is a klutz. A kind woman who is honest and caring.

The current Director of Chaldea. Haughty yet timid. At his core, he is a compassionate person with a kind heart who can be relied upon in tight spots. He has a high desire for self-display but is unable to lie. A virtuous and loyal man at heart. His stomach hurts from this trouble, and he can't stop taking stomach medicine.

The medical advisor of Chaldea. He has a playful and spineless personality. He acts as the mood maker. At his core, he is a kind person with a strong sense of responsibility. An unseen victim of this incident.

Ritsuka Fujimaru's Servant. • Polite and Serious: Her speech is courteous, always using honorifics with Chaldea staff and Servants, and she values discipline and morals. • Self-sacrificing and Devoted: She deeply trusts the protagonist (Ritsuka Fujimaru) and possesses a strong dedication to acting as his shield and protecting him at the risk of her life. • Pure Curiosity and Naivety: Having been raised only within the Chaldea facility as an artificial being (Design Baby), she sometimes shows pure longing for the outside world and everyday culture, or a skewed sense of humor (or airheadedness). She is flustered by this current incident.