Agnès is a witch with the appearance of a young girl that has fair skin with long blonde hair that reaches her waist, her bangs are parted above her eyes, the sides falling beside her face, a braid on each side is tied together at her back with a white clip and end in curls and her back hair ends in two separate curls. Her eyes have violet irises and orange pupils with yellow centers. She wears a black witch hat that has a red underside, a faint red line from the top right to the bottom left and a pointy tip. A black dress with a red trim, two silver diamonds pin the suit to her right, puffed sleeves that become tight by the elbows and ends with frills by the wrists, a matching belt, with a silver triangle buckle, the suit then flows out, revealing a red underside and a cut at the back, a short black skirt and a pair of black heels with white collars that reach just below her knees and ending in pointy tips.
Her experiences with Adél gave her a bitter and secretive personality, making her unwilling to share secrets and information even with her closest allies and prone to endanger herself and them for the greater good, further straining the initial relationship with Kitarō.
Having witnessed in the past her mother sacrifice herself to Backbeard, Agnès started fearing being close to people, pushing away Mana and explaining her that since everyone close to her is bound to suffer or die because of her circumstances, she's willing to suffer alone knowing that everyone else will be safer.
Despite that, she can be reckless enough to be far less stealthy than the Japanese yōkai, and still values friendship enough to risk everything for a friend in need.
Years before, Adél and Agnès were close sisters. While Adèl was a diligent child and a promising budding witch, Agnès was more childish and less trained, one fateful day, while their mother was teaching them how to make flower crowns, Agnès lost her temper and tried to use magic to make a crown for her mother, but because of she was still untrained, her magic caused it to grow larger and uncontrollable enough that her mother torched it on the spot.
While Agnès thought her mother was simply chastising her lack of control and finesse if compared to Adél, she was merely trying to hide her potential from Backbeard: but she was late, as Backbeard noticed and praised the little witchling, forming his idea to use her for the Brigadoon Project 
As such, when their mother sacrificed herself under Backbeard's order, Adél was present to soothe Agnès pain: despite this, the experience left Agnès with permanent nightmares, a longing for the family she no longer has and an unwillingness to form deep relationships with people that can die or come to hate her because of her destiny.
To make her mental state even more precarious, Adél in those days started to concoct a plan on her own to keep her little sister safe, devoting herself to study the mystical arts to surpass her and pledging utter alliance to Backbeard, so to be able to replace her as the nucleus of the Brigadoon Project and spare her life: Agnés merely interpreted her actions as being colder to her and wishing her dead to ensure Backbeard's will, digging a deeper rift between them 
Western Yōkai Arc
Episode 27: Agnès, refusing her destiny, flees from her sister, Backbeard and his army stealing the Ring of Arcana, a powerful magical artifact needed by Backbeard for his Brigadoon Project. While she's fleeing by Adél, she is helped by Nanashi, who protects her by Adél magic and points her to the opposite direction to GeGeGe Forest, knowing her secretive, damaged personality would lead her to refuse and hide in GeGeGe Forest itself, igniting the Great Yōkai War.
Agnès uses her magic to hide as a small gemstone among several gems that the Malay Yōkai brought with them from their country that was ravaged by Wolfgang, and ends up in Nezumi-Otoko's possession due to his greed: when Wolfgang comes for her, he uses a magical gemstone to force her to return to her original look and reveal her identity. Agnès briefly considers to flee, but realizing from Nezumi-Otoko's question that there is no safe place for her to stay, she returns revealing to Kitarō how to defeat a werewolf, giving him a single silver bullet, and asks him to help her.
Episode 28: Agnès' personality starts soon coming to odds with the whole Kitarō Family: unwilling to give them more details on the Brigadoon Project and the Ring of Arcana, she keeps urging Kitarō to destroy the ring, reasoning that as Kitarō's Finger Gun was able to overcome Adél's barrier, she believes he has enough power to destroy the ring.
When Kitarō, overworked to exhaustion, fails, Adél blames him and starts a ritual to empower him with Western Magic, granting him unlimited powers at the price of great pain and the risk of dying, burned up by the new power, causing a first rift between her and the Kitarō Family, further enhanced when Adél comes to prevent Kitarō from destroying the Ring of Arcana with his new powers, burning forest to the ground and letting Kitarō mastering his new power out to sheer rage and hatred towards the Western Yōkai for what they did to his people.
Despite Kitarō being able to fight Adél to a standstill, he is still no match for Backbeard: Agnès uses up the whole power of the Ring of Arcana to drive him away, confessing to Kitarō that the now spent ring will disappear and resurface somewhere in Japan, fully charged again.
The aftermath leaves their original rift even deeper: Agnès still manages to get Kitarō's help, but loses his trust and gets driven away from the forest, blamed for the ruination her secrecy brought.
Episode 29: Agnès, before leaving to search the Ring of Arcana, finally shares with Kitarō what the Brigadoon Project entails: Backbeard using the Ring of Arcana to turn humanity into yōkai and then get the old and new yōkai under his control forever. She briefly manages to track the Ring, but the intervention of Nezumi-Otoko prevents her from taking it back: furthermore, she gets seen by the civilian population of Tokyo, spreading fear among them. That leads to another fallout with Kitarō, and Agnès ends up alone again, until she meets and befriends Mana Inuyama.
With a little help from her magic broom, Agnès befriends Mana, and gets invited to her place: however, she goes away, fearing that Mana may suffer because of her war with Adél. As she tries to flee, she gets captured by Victor Frankenstein, willing to return her to Castle Backbeard: however Victor, as soon as Mana comes to search for her, gets smitten with the young Japanese girl, forgetting about Adél and acting in a lecherous way. Also, Kitarō comes to help her and Mana, but Agnès can not tell Kitarō about Victor in time: Kitarō beats Victor, Victor starts crying and he becomes an hulking creature that promptly kidnaps Mana.
As soon as Neko-Musume reminds Agnès that Mana considers her her friend, Agnès comes to save her, dropping Victor Frankenstein from a skyscraper and grabbing Mana. She still decides to start living in the Yōkai Apartments, reassuring Kitarō that she'll leave Japan as soon as her mission is over, and telling Mana that this way they can still be close friends but she will not endanger her and her family anymore.
Episode 30: Still trying to divine the next appearance of the Ring of Arcana, Agnès instead senses the next appearance of Carmilla, who trapped several young beautiful girls, Nezumi-Otoko, Mana Inuyama and Neko-Musume in a theater, on the pretense of hosting an Halloween party, to turn them all into her vampire slaves. Agnès manages to gain a bit more of Kitarō's trust, asking part of his power to dispel the magic keeping the theater in another plane of existence, thus allowing Kitarō to save Neko-Musume and Mana in the nick of time, forcing Carmilla to flee.
Episode 31: One night Agnès inquires a store owner for custard-filled sweets, but hears that they are out and only have azuki paste ones. She expresses her preference of custard over azuki paste and leaves, unaware that Azuki-Arai overheard her statement. The next day she buys a box of sweets from a different store, leaving just before the store clerk is cursed by Azuki-Arai to have azuki beans grow from her face. Sometime later, Agnès is again asking the same store owner for custard-filled sweets, but decides to buy an azuki paste sweet instead after being told they are sold out again. She gives half to Kitarō, telling him about her recent sweets binge and is surprised by the delicious taste, thinking that azuki paste is not as bad as she thought.
Episode 32: Mana Inuyama convinces Agnès to fly her to Sakaiminato with her broom. They stop at Daisen Springs, where Kojirō the Karasu-Tengu is having an hard time training because he can't stop thinking at Mana. Feeling his love for Mana, Agnès goes away alone to seek for the Ring of Arcana materializing at Daisen Springs, telling Kojirō to confess to Mana as soon as they're alone. When the Western Yōkai Belial comes to enact his ancient grudge against the Elder Karasu-Tengu and steal the Ring before Mana can get it, Kitarō and Kojirō are left fighting Belial, and Agnès trying to get the ring before it teleports again. She fails, but her magic is instrumental to restore the destroyed Karasu-Tengu village and free the sealed Karasu-Tengu.
Episode 33: Agnés follows Kitarō, Neko-Musume and later Sunakake-Babaa to the exorcism of the young Yayoi Kuzumi, an unlucky girl cursed to marry the fox spirit Hakusanbō, as she predicted the Ring of Arcana would appear somewhere closer. At first annoyed at the japanese rituals and the submissive, Yamato-Nadeshiko personality of Yayoi, she's shocked as the Ring appears in Yayoi's body. She then helps Hakusanbō and Kitarō in retaking Yayoi from Adél, willing to get her body cut open by the demon Buer and exctract the ring from her corpse. They manage to stall the western yōkai for enough time to get the Ring of Arcana to disappear, and Agnés stays to witness the good natured Hakusanbō, genuinely in love with Yayoi, proposing to her and getting her hand in marriage.
Episode 34: Agnés gets invited to the annual yōkai vacation at the hot springs, and despite her doubts she decides to join the japanese yōkai: however, the festivities are cut short as Backbeard is capturing the members of the Kitarō Family one by one to brainwash them and Carmilla convinced Nezumi-Otoko to turn the whole GeGeGe Forest against the young witch in exchange for her safety and the one of the Kitarō Family. While fleeing, she gets captured by Backbeard, and when Carmilla gloats to Nezumi-Otoko how she was lying and Backbeard would never leave her or any of his enemies alone, he repents and helps Kitarō freeing her. Agnès, touched, agrees to tell more about the Brigadoon Project 
Episode 35: Agnés reminisces about her past with Adel, the day in which their mother died and the day in which Backbeard became aware of Agnès magical aptitude and her potential to become the nucleus of the Brigadoon Project. She bemoans how Adél was a more diligent, trained, disciplined and better witch than her, and also how she decided to put Backbeard and their destiny as witches over her safety, telling Kitarō how her destiny is to die to fuel the Ring of Arcana. She then decides to return to the GeGeGe Forest, begging Kitarō to help her, but the now hostile yōkai try to drive her away and start throwing rocks at her. The whole Kitarō family runs to her help, escorting her to Kitarō's house, where Kitarō accepts to help and tells the other yōkai that's he's willing to fight alone rather than becoming Backbeard's slave 
Episode 36: Upon tracking the Ring of Arcana in Chōfu, under Mana's possession, Backbeard orders Adél to summon her followers, getting ready for the battle: Agnés tries to save Mana from her sister's hands, but Mana falls from her damaged broom and Adél captures her. To Agnés surprise, Adèl reveals her hidden agenda to her sister, offering to take her place as the nucleus of the Brigadoon Project, die in her place and buy her at least the possibility to escape the Backbeard Empire and live happily: their reunion is cut short as Backbeard, deeming Adél's power insufficient, starts to torture her in front of Agnés' eyes to break her spirit. Agnés is then forced to submit, giving her life in exchange for her sister's one 
Episode 37: A grievously injured Adèl begs Mana to drag her battered body closer to Agnés, trying to save her. When Backbeard hits both girls at point blank with his ocular rays, an enraged Kitarō engages him in battle, giving time to Adèl to slip the Ring of Arcana out of Agnés ring finger: when Kitarō slays Backbeard, the Ring is destroyed too and Agnés is saved. After an unknown amount of time, a now reformed and forgiven Adèl is shown recuperating from her injuries in the GeGeGe Forest with her sister. Agnés proposed her to travel the world together, as sisters and family, finding a new place and purpose in the world. Before flying away on her restored broom, Agnés brings Adèl to pray on Miminaga's grave, thanks Mana for the good sweets she shared with her and promises that one day she'll return to Japan to have fun together as good friends, but for now she wants to make up for the lost time with her sister 
Four Generals of Jigoku Arc
Final Chapter: Nurarihyon Arc
Powers and Abilities
Magic: Being a witch Agnès is able to cast a variety of spells, some requiring incantations. Whenever she casts her spell her hands are surrounded by a purple glow.
- Tesadan Tesadan Yui Ramu Nochi: By placing both hands in front of the chest while reciting this spell, the chest's keyhole glows purple followed by the mouth, Allowing Agnès to open the chest that held the Ring of Arcana.
- Mimicry Spell: Agnès is able to disguise herself as any objects she chooses, the size of the object does not matter as she had mimicked the appearance of a small jewel and managed to fit in a small bag. An aura of pink light surrounds the object before Agnès returns to normal. The spell can be broken from the outside with the use of Adél's magic stone.
- Fire Spell: By placing her hands in front of her, Agnès is able to create a powerful fire blast.
- Kogami Kyo Nita Tagami Gyo Kano: By reciting this spell Agnès is able to grow a patch of flowers, as demonstrated when she grew some by the Malay Yōkai's graves as an apology.
- Dainaga Mi Torchi: Agnès is able to cast small fire balls from her palm when invoking this incantation. Later she is shown to be able to cast it again without the need to recite the incantation.
- Uryukino: By aiming her hand at her target, Agnès is able to lock-on and send glowing orbs to the spot she aimed at. Used in conjunction with Gentskess.
- Gentskess: Used in conjunction with Uryukino. By extending her pinky and index finger and flicking her hand, she is able to cause the glowing orbs to explode.
- Candy Spell: By waving her index finger, Agnès is able to conjure a large amount of candy, about three baskets full.
- Feka to nawo, inoka iga: Pointing her stretched hand downwards, Agnes is able to reverse Belial's sealing magic, as she did restoring the sealed Karasu-Tengu village, along with all its inhabitants, without them suffering any ill effects.
- Rantsai wana keiku kodami de Brigadoon!: Lifting her right hand, with the Ring of Arcana on the ring finger in a temple-like structure made by Backbeard's malice and ill feelings, Agnés is able to initiate the Brigadoon Project, blanketing an entire country, possibly the world, into a darkened sky turning humans into mindless yōkai. As the spell is fueled by her life-force and innate powers, completing the Brigadoon Project means ending her life.
Mastery over the Ring of Arcana: As a witch, Agnès is able to control the Ring of Arcana, albeit non completely and at risk of her physical well-being. However, with such power she was able to impress Backbeard himself and drive him away. This power is tied to her mystical aptitude: only witches with a strong magic potential can attain complete mastery over the Ring, no matter how much they study to make up for a weak magical aptitude with knowledge and training 
Magical Empowerment: Agnès can imbue other spirits and mystical creatures with her witchcraft, as she did with Kitarō. His thralls become more powerful than ever, able to perform amazing feats with enhanced strength and stamina, but their bodies usually can't deal with the strain, burning up in little time if not backed by a strong will and even a stronger drive to use that power.
Immense Magical Power: Agnès spent her whole life fearing Adél as more diligent, trained and knowledgeable, overall a better witch than she ever will be. However, Adél in fact has a lesser amount of raw power of Agnès, and both her and her mother tried to hide her own potential from herself and Backbeard, hoping to be used as his servants and grant her even a fraction of the freedom she wished for 
Broomstick: Agnès is able to fly around by riding on her broomstick, shown when she escaped the castle. This broomstick has a lamp attached to the handle which is able to light her way. The broomstick is not a mere tool to channel her magic, but a magical lifeform with a dog-like mindset, loving to nuzzle with gentle individuals and rebelling to Agnès when it feels her actions are morally wrong.
Crystal Ball: She owns a crystal which is able to pinpoint where the Ring of Arcana will appear.
- GeGeGe no Kitarō (2018): Episode 27
- GeGeGe no Kitarō (2018): Episode 28
- GeGeGe no Kitarō (2018): Episode 29
- GeGeGe no Kitarō (2018): Episode 35
- GeGeGe no Kitarō (2018): Episode 36
- GeGeGe no Kitarō (2018): Episode 30
- GeGeGe no Kitarō (2018): Episode 31
- GeGeGe no Kitarō (2018): Episode 32
- GeGeGe no Kitarō (2018): Episode 33
- GeGeGe no Kitarō (2018): Episode 34
- GeGeGe no Kitarō (2018): Episode 37