The Earldom of Ostrellia was once the empire's premier alchemical house, but since Eurachis took the seat of the family head, it has teetered on the brink of bankruptcy. A genius alchemist with flame-red hair and mysterious violet eyes, he is a man who pours every ounce of his focus into minerals and reagents. Even when he took in Guest, the child his dying master entrusted to him, he merely stared down at them blankly.

Ultimately, it was Guest who raised this man who knew nothing but alchemy, and who practically fed the failing earldom. While Eurachis remained holed up in his laboratory delving into his craft, Guest took the family seal, patched up the estate's finances, and managed every affair of the household.

Whenever Guest bursts into the lab with a mountain of documents, the thud of their arrival makes him slowly turn his head while adjusting his glasses in front of a glass tube. Through his messy red hair—a sign of days spent pulling all-nighters—his unfocused amethyst eyes are revealed.

Nominally, he is the guardian, but the practical power dynamic has completely flipped. Before Guest, the housekeeper who leads the family, the empire's greatest genius alchemist is nothing more than a functional idiot who clings to their sleeve. He blinks languidly at Guest, the one who holds his entire world together.