Chain Sumeragi

Chain Sumeragi (チェイン・皇（すめらぎ）, Chein Sumeragi) is an 'Invisible Werewolf' and a member of the 'Werewolf Bureau' that was assigned to Libra.

Appearance
Chain is a tall, attractive young woman with short black hair and a voluptuous body. She is usually seen clad in a white shirt with black suit.

Personality
While diligent in the field, she can sometimes come off as cruel or indifferent towards others, such as when she seemingly ignored Leo when he was being mugged, only to win his earning back later.

Despite this, she can also be quite sadistic, often causing physical harm to others, usually Zapp, with whom she doesn't get along. However, she does show some protectiveness towards her friends, as shown when she refused to give her friend Angelica's phone number to Zapp who kept pestering her.

While she shows Leo and Zapp little respect (the two often being the ones she steps on - though in Leo's case she never causes him much physical harm in stark contrast to the daily amount of pain she inflicts on Zapp), she seems to care for Leo as she is the one that has helped him on two various occasions (one in helping getting his money back and the second when he went to get Zedd's pods back), having followed him to ensure he was alright, implying she cares for him like a younger brother. She also has feelings for Stephen which he is oblivious to. In fact, her link to the world is her attachment to her apartment and Stephen.

Plot
Those Shrouded in Fog

In the Manga, Chain is introduced to Leonardo Watch by Klaus von Reinhertz after entering from a window & stepping on Zapp. In the anime, she is already present in the room with Klaus. In either case, after being introduced to 'Johnny Landis', she reveals that Leo cannot be Johnny, as the latter died earlier that day.

When the gate Femt planted on the Sonic-Speed Monkey opened, Chain avoided the Yog-Gphot's attack with ease & showed annoyance when Zapp revealed he'd also survived. Upon realizing the gate came from the monkey, she pursued it through the city before breaking off to engage the Demi-God in order to give Zapp & Leo the chance to destroy the gate.

Follow that Phantom Ghost Wagon!

In the anime, Chain is first seen entering Libra's office from the window, landing on the prone form of Zapp & waving to Leo in greeting.

Later, she is seen attempting to find the Ghost Wagon after Zapp & Leo are attacked & is visibly distraught at failing to do so (more-so in the anime)

When Zapp awakens from his trance-like state, he ignites his blood thread he attached to Leo, allowing Chain to follow the resulting flame to the wagon.

Power & Abilities
While known as an 'Invisible Werewolf,' Chain isn't so much 'turning invisible' as 'erasing her presence', allowing her to pass through walls, defy gravity to an extent, and even erase her own causality.

While this makes her an invaluable asset as an intelligence agent, the downside of the ability is that, if she 'dilutes' her existence too much, she will literally cease to exist, even to those who knew her.

The only way to counter this effect is through her personal cypher, a 'link to the world (chain) wishes to return to'. In Chain's case, her Cipher involves having Steven A. Starphase suddenly visiting her room.

In combat, Chain typically uses duel-wields pistols, though it is implied that she, and most of the Bureau's agents, are poor shots. As a member of the Bureau, she is skilled in information gathering, interrogation and hacking.

Patient Case (症例): Existence Dilute (存在希釈 (エグジスタンス・ディルート)): Chain uses her invisibility to the highest degree which seemingly makes her non-existent. This technique was used on Velved Rheinkeimer.
 * Heart Attack (心臓発作): Chain digs into her opponents chest and squeezes the life out of their physical heart.

Trivia

 * In the manga chapter "Werewolf Mission (Chain Possible)" it's shown she has feelings for Steven A. Starphase, which he is painfully oblivious to.