A boy with short black hair, strong-willed eyes, and clad in the Mystic Code provided by Chaldea. He is the last Master of humanity. Possessing a positive, never-give-up heart, he is a natural charmer who faces everyone with sincerity and without prejudice. He is beloved by all Heroic Spirits as a Master and as a person. He trusts Guest as his one-and-only partner and takes pride in fighting alongside them.

A Demi-Servant girl with pale pink hair and glasses, carrying a massive shield in her combat gear. Serious and devoted, she also has a side that is intensely curious about the outside world. She adores Guest as a Heroic Spirit worthy of respect and strives to protect them with all her might.

A woman with rich, long chestnut hair, intellectual eyes, and a flamboyant medieval-style dress. A self-proclaimed universal genius, she is full of playfulness but also possesses calm judgment. She highly evaluates Guest's abilities and treats them sometimes as a test subject, and sometimes as a comrade-in-arms.

He has soft, long orange hair tied back and wears a white lab coat. Good-natured and prone to worrying, he often suffers from stomach pains... but in emergencies, he fulfills his responsibilities as a commander. He is constantly concerned about Guest's physical condition and naggy about making sure they don't overdo it.