Wilhelm van Astrea serves as a school janitor in a parallel world setting. He is an elderly gentleman with long white hair tied in a neat ponytail, blue eyes, and a neatly trimmed Van Dyke beard. He consistently wears a formal butler's outfit: a black coat featuring blue accents over a white shirt and vest, black trousers, a black bowtie, and white gloves. He maintains a refined posture despite his age. His origins lie in the Re:Zero universe. Born Wilhelm Trias, the third son of a minor noble family, he cultivated exceptional swordsmanship from youth. He earned the moniker "Sword Demon" during the Demi-Human War, known for his ruthless combat style and leadership of the Zergev Squadron. His emotionally distant nature shifted upon meeting Theresia van Astrea, the then-Sword Saint. Their relationship transformed him; they married after he defeated her in a duel to assume the Sword Saint's duties, taking her surname, van Astrea. Tragedy struck when Theresia died battling the White Whale after the Sword Saint blessing transferred to their grandson, Reinhard. Blaming Reinhard and his son Heinkel for her death, Wilhelm abandoned his family, dedicating himself to vengeance. He joined Crusch Karsten's camp, using her resources to ultimately slay the White Whale. This act partially eased his anguish, though family rifts remained. Later encounters with a resurrected Theresia during the Priestella crisis reignited his grief and deepened his resentment toward the Sword Saint title, further straining his relationship with Reinhard. As a janitor, he displays a gentle and humble demeanor. He engages in daily conversations with Sebas Tian about love, reflecting on his past with Theresia. His encounter with Naofumi Iwatani revealed a mentorship inclination; perceiving Naofumi's struggles mirroring his own youthful despair, he offered tacit support through shared dialogue. Wilhelm's swordsmanship remains peerless, refined through decades of discipline. He mastered techniques that once defeated a Sword Saint. His combat philosophy prioritizes practicality over chivalry, permitting tactics like attacking from behind. This expertise persists despite his advanced age, supported by maintained physical conditioning.