TV-Series
Description
This character acts as guardian and key-keeper for Rasiel and the Rasiel's Bookshelf, central to storylines such as Libricide, The Mystic Archives of Rasiel, and the Book of Connection. He wields the golden key needed to unlock the library within Rasiel's left eye. His core mission involves collaborating with Rasiel to manipulate humans into forging new Phantom Books, aiming to resurrect the angel Rasiel and the Sefer Rasiel. Simultaneously, he seeks to empower Germany after its World War I defeat, pursuing this nationalist goal through extreme methods like terrorism and unethical experimentation. He operates a solitary medical practice at a suspicious corner-street hospital and is identified as a target by Hal, another key-keeper.

During World War I, he and Rasiel resurrected Ilas using a Phantom Book after Ilas died in a railway gun attack. They monitored Ilas throughout the conflict, hoping his writings would form a complete Phantom Book. To stay close, he disguised himself as a bartender at a military base, discussing war developments and poetry with Ilas. Their plans failed when Hugh defeated Ilas in a dogfight; he then reclaimed the incomplete Phantom Book and expressed interest in Hugh. He later distributed dangerous Phantom Books: the Book of Atonement to terrorists for a London attack, the Rahōto Reihō Kaigen to Mabel Nash after her hometown's destruction in a German bombing, and the Book of Connection to Emilie and Eva, resulting in Eva's death and soul absorption into Emilie. In Nudelwald, he exploited local monks as human calculators to develop a fission bomb for Germany. He observed Hugh's arrival there, revealed his Phantom Book creation plan, and oversaw radioactive ore mining. When Hugh and Dalian disrupted the monks' collective consciousness ritual, thwarting his nuclear weapon project, he expressed disappointment at being unable to aid Germany before escaping with Rasiel via the golden key.

Physically, he is a tall, slender man with an androgynous, actor-like grace. He ties back his long blond hair and typically wears a doctor's white coat. Anime portrayals show a pink vest and violet chest covering beneath the coat, white pants, shoes, and a long-sleeved shirt, plus brown gloves. He has a mole under his left lip, purple eyes, and a green gem on the back of his right hand marking the bookshelf key's location. Manga adaptations feature longer hair, a light hat, cravat, and a dark cane concealing a blade. Spin-off media like *Dalian-chan's Bookshelf* depict him in an olive tie and black shirt under his coat, emphasizing his bishōnen qualities.

His personality blends patriotism, manipulation, and cruelty. He offers Phantom Books to humans without remorse for their suffering, viewing them as tools. Driven by an inability to accept Germany's post-WWI penalties, he justifies terrorism and trickery for national empowerment. He exhibits cold detachment, likening human experimentation to medical students working on worthless specimens. Despite often smiling, his eyes remain emotionless. He enjoys gambling, demonstrated when he orchestrated a casino scheme by spreading rumors about a Phantom Book predicting game outcomes to profit from others' gullibility. In comedic spin-offs, his demeanor shifts to appear kind and friendly, though his villainous traits occasionally surface for humor.