Chi

Kai (カイ) (Χι), formerly known as Karen von Herzog (カレン・フォン・ヘルツォーク) is a member of Shadow Garden who works as Epsilon's direct subordinate, which she formerly a member of the Velgalta's Seven Blades from Velgalta Empire and a Cult of Diablos' defector as Named First Children, titled Shooting Star (流星ながせ). Thanks to her valuable intel on the Cult's knowledge, she effectively rose through the ranks until become one of the Named Numbers.

Appearance
Kai is an elf with short blonde hair and emerald green eyes with an athletic build and a modest chest. Her right eye has an eyepatch which is hidden behind her bangs due to it being gouged out by Sergey Gorman.

As a member of Shadow Garden, she wears a dark slime bodysuit, stylized with gold decorations, a short shoulder cape, and a jacket. The design of her suit is near identical to Omega's, but her counterpart doesn't have a shoulder cape.

She sometimes decides to dress more in men's clothes, since according to her, it helps her to collect information in different details, other than what she likes as woman.

Personality
Little is known of Kai's past or personality, other than she was abandoned like the others in Shadow Garden when stricken with Demon Possession and became loyal to their cause of destroying the Cult of Diablos.

Kai, formerly known as Karen von Herzog, was a former member of the Velgalta's Seven Blades she was also a First Child of the Cult of Diabolos. When she was stricken with Demon Possession, she ran to a remote village in the region of Madlid chased by another member of the Vegalta's Seven Blades, Sergey Gorman.

While active on Shadow Garden missions, Kai is steadfast in her duties, executing her objectives to their fullest. When Kai is in her civilian dressing, she is seen to be friendly toward citizens and her coworkers, Omega especially as the two are partners and direct subordinates to Epsilon.

Web Novel
Kai is a quiet person, she only responds to orders from her superiors with short sentences or only responds with nods. She behaved like that not because she was disobedient to her superiors, but because she was a social phobic person.

She has great anxiety and fear when interacting with other people. This was proven when he was ordered directly by Shadow, Kai responded with her body shaking in fear. However, Shadow immediately overcomes this by having a relaxed conversation containing advice for her.

Powers & Abilities
Before defecting to Shadow Garden, Kai was the most powerful warriors as an Named Child, considering "First Children" who have provided outstanding contributions to the Cult of Diablos until she even become a member of Velgalta's Seven Blades. Thanks to her exceptional prowess and combat ability, she quickly rose through the ranks and making her one of the double-digit Numbers, which she are given a Greek name. She is eventually assigned to be the direct subordinate of Epsilon, one of the Seven Shadows.

Physical Abilities
Kai, like many before and after her joining, trained daily to improve upon her physical prowess. Such is necessary to be ready for a fight or to retreat to safety. This includes self-defense, martial arts, and strength training.

Swordsmanship
Before joining Shadow garden, Kai as Karen, had very strong magical and swordsmanship skills, being a "Named Daughter" of the Cult of Diabolos. Shortly after being rescued and healed by the members of Shadow Garden, After being retrained, Kai's abilities increased strongly, along in part with her use of magic, which made her one of the reasons why she was named, to the Named Numbers of Shadow Garden.

Magic
Kai is an expert in magic, as a former member of the Diablos Cult, and being a "Named Son", she had great magic power, upon being cured of her Demonic possession, she gained strong control of magic, since she maintained her slime suit during the magic distortion effects of the Holy Sanctuary infiltration. Such is a requirement given Epsilon's renown within Shadow Garden for her refined magical control.

Quick Flash
A speed-enhancing ability, derived from early practice of speed magic. Before joining Shadow Garden, Kai as Karen, had said ability, as a former member of the Devil Cult, as a "Named" Daughter.

Improved Quick Flash: After being rescued, healed and joining Shadow garden, her ability improved more effectively, thanks to the teachings and training, which Shadow taught the Seven Shadows who then in turn taught this to the first members who they came after them, as was the case with Lambda.

Standard Equipment

 * Slime Bodysuit: A standard issue in Shadow Garden, with Kai's having notable decoration to express higher rank and authority within the command structure compared to the rank-and-file.
 * The Rolapoid: An instant camera for missions of espionage, a reverse-engineered technology from Shadow Wisdom by Eta.

Trivia

 * According to the director's tweet about Kai's illustration, the symbol to represent her name is χ, which is the 22nd letter of the Greek alphabet. In fact, the very first sentence from the Wikipedia page for the letter is already explains how to pronounced it.
 * Kai is the first Web Novel character to have a canonical debut appearance in Anime and Games.
 * Apparently it was Kai's name who was reveal to be the defector from the Cult of Diablos that Nu had previously mentioned in the first light novel, before being officially debuted.
 * Kai actual age as such is unknown, but according to the game, when she was rescued by Gamma and Eta, Kai was already an adult, so her age-level appearance ranges from 20 to 21 years old.
 * Despite being women, Kai and Omega like to dress up as men occasionally. According to the two, this is so they can have other means of information gathering, unlike other Shadow Garden members. Although sometimes, they crossdress their clothes for fun.
 * Originally, according to some words from the author, when he was writing the characters of Kai and Omega, he had thought of making them the only men in Shadow Garden. But the idea was discarded, seeing the strong controversy that would arise with the story developing in the community. This is why the characters wear men's clothing, reflecting in some part of the author's discarded ideas.
 * Erroneously at the beginning, Kai and Omega were mistranslated as men in the Web Novel, before the anime premiered, which caused strong controversy in the Latin American and partly North American community when it was announced that all possible characters would be taken from the 3 versions of the story: the Manga, Web Novel, and Light Novel. But that would follow the Light Novel story route to which those translated were not fully corrected, until the full release of the anime and the game release.