Halter is generally portrayed as an affable and approachable individual who rarely loses his temper. Despite his imposing appearance, he is shown early on to be a cautious and caring figure, often worrying about those around him. His unwavering loyalty to Marie Bell Breguet defines much of his character, as he fulfills not only his role as her bodyguard but also assists her in administrative and secretarial matters.

As the primary adult figure within Second Upsilon, Halter frequently acts as the voice of reason. He provides guidance and perspective to his younger companions, mediating when their talents or conflicts overwhelm them. This role positions him as both a mentor and stabilizing influence.

Halter is also deeply principled. When he learned of the Army’s plan to sacrifice Kyoto’s population of twenty million, he responded with outrage, underscoring his strong moral convictions.

During the Shangri-La Arc, another side of Halter is revealed, one that is strategic, deceptive, and difficult to fully read. His legendary reputation as “Overwork” stems not only from his skill but from his unique approach to mercenary work: he prioritized the long-term security of his employers, even acting beyond their immediate orders. For example, he would eliminate individuals who intended to undermine or betray his employers in the future. This foresight and loyalty distinguished him from ordinary mercenaries, earning him the trust of the Breguet family and solidifying his place as one of the most respected figures in his field.

Vainney Halter is an imposing figure, standing over two meters tall and described as a burly, stalwart man. He has brown eyes and short grey hair kept in a buzz cut, distinguished by two shaved lines running along the left side of his head. Naoto Miura once compared his gait to that of a carnivorous wildcat, emphasizing both his physical presence and predatory grace.

His typical attire consists of a red collared shirt worn beneath a business suit, with the sleeves usually rolled up. He also wears black gloves and sunglasses, further adding to his intimidating appearance.

Vainney Halter is an eighth-generation mechanized human, outfitted with advanced cyborg components developed by the Breguet family. His modifications surpass the latest market models then at the sixth generation, with the seventh only beginning to appear granting him strength far beyond that of an ordinary human. With this enhanced body, he is capable of destroying combat automata with his bare hands. Though his artificial body sacrifices physical sensitivity, it provides overwhelming power and durability. Halter underwent mechanization in his youth and later rose to the rank of Geselle as a clocksmith, granting him the expertise to assist the Meister Guild in complex repairs.

After sustaining catastrophic damage, Marie briefly connected his brain to a war machine, during which he became nearly invulnerable and was able to fight alongside Second Upsilon’s Initial-Y units against military-grade automata. Following these events, he was eventually restored to his original human form.

During the attack on the Shangri-La grid, Halter demonstrated his combat prowess by single-handedly annihilating Arsenal’s forces. Even after being disabled by an electromagnetic pulse, his sheer willpower allowed him to continue fighting despite his body being rendered immobile. His extraordinary resilience is further proven by his survival of multiple EMP strikes, after which Marie was able to repair him.

Beyond his physical abilities, Halter’s greatest strength lies in his intellect and tactical foresight. He is known for devising plans that leave both allies and enemies unwittingly moving according to his design, revealing the depth of his strategic mind only when it serves his purpose. As he explained to Vermouth, his approach to mercenary work extended beyond fulfilling immediate contracts: he eliminated threats before they could arise, even targeting those who might one day seek to undermine his employer. This foresight and ruthlessness contributed to his reputation as the legendary mercenary “Overwork.”

Breguet Family
Halter is employed by the Breguet family as Marie’s bodyguard, a role that reflects their strong trust in his loyalty and abilities. They continue to believe he will protect Marie even after her staged death. Halter himself acknowledges their generosity in compensating him, though he warns Marie not to emulate her elder sister, whom he considers a poor influence.

Marie Bell Breguet
As Marie’s protector, Halter is devoted to ensuring her safety and well-being, often placing her needs above his own. Their bond extends beyond duty; Halter has openly declared his willingness to sacrifice his life for her. Marie, though usually trying to hide her feelings, demonstrates her deep care for him, breaking down in tears when she believed he had been killed in action.

Hannes
Halter and Hannes work alongside one another under Marie’s leadership. While little is revealed about their personal interactions, the two display mutual trust and respect, particularly during their cooperation in the Kyoto Grid purge incident.

Naoto Miura
Halter maintains a positive relationship with Naoto, recognizing him as a genius on par with Marie. He demonstrates an ability to motivate Naoto when necessary, often knowing exactly what to say to push him into action.

RyuZU
RyuZU generally regards Halter with tolerance, interacting with him in a professional manner. During their escape from Japan, the two exchange philosophical observations about fate, leaving Halter impressed by her capacity for abstract thought. Their relationship deteriorates temporarily when Halter, under the coercion of Kiu Tai Yu, kidnaps Naoto. After returning and apologizing, RyuZU entrusts his fate to AnchoR but warns him never to betray them again.

Vainney Halter’s name is a reference to the real-life French watchmaker Vianney Halter, known for his intricate, innovative timepieces that often draw inspiration from steampunk and mechanical aesthetics. This naming aligns with Clockwork Planet’s overarching theme of horology and automata.

His codename “Overwork” reflects his relentless efficiency as a mercenary, while the nickname “Oberon,” given to him by Shirley, alludes to the king of the fairies in Shakespeare’s A Midsummer Night’s Dream. The title “Boss,” used by Vermouth, emphasizes his commanding presence and leadership qualities.