|Spoiler Alert: This article or section contains details about plotlines not covered in the anime. Do not proceed unless you wish to be spoiled. |
While observing, Charlotte was a very small pitch-black spider with four deep crimson-red eyes and eight slender legs. Most of the time, she was less than five millimeters in size.
However, she was actually a giant spider that was over two meters in overall length and had a tough-looking carapace. In this form, she had a jet-black shell that gleamed like the rasta colors, tinged with gold in the light. Her claws growing on her eight legs looked like black crystals. Two of her legs were visibly larger and their claws were long enough to bear resemblance to swords. Charlotte also had thick, short fangs growing from her mouth.
Charlotte had the voice of a calm, wise, gentle and warm adult woman.
As an observer, Charlotte believed that it was her duty not to interfere with her observed parties and also believed that she did not have any emotions, nor had she ever been interested in the parties that she had to observe. Only after meeting Kirito and Eugeo did she start to change. She became influenced by them and began showing certain emotions, like anxiousness, curiousness and frustration. She had also decided to interfere with certain events on multiple occasions to help the two young men on their journey, using excuses, like her interference making her observations more efficient, to justify her actions. Moreover, after meeting the two mysterious young men, she spent more time pondering about various details, instead of just observing them, like she used to do until then. Charlotte grew so attached to the boys that she continued following them even after being relieved from her duty and even sacrificed her life to buy enough time for Cardinal to come.
Charlotte's main wish was to finally return to a corner of the Great Library Room that she used to live in. She also expressed a wish to see the land of the Dark Territory to confirm its existence with her own eyes.
Charlotte used to be one of the numerous large beasts that were capable of speaking in the Common Tongue, but after Quinella started eliminating such monsters or using them as resources for weapons, Cardinal sheltered all the ones that she could save, including Charlotte. Due to Charlotte having a modest pseudo-intelligence engine and having high stats, allowing her to shrink without suffering any damage, Cardinal assigned Charlotte to look for possible collaborators for about 200 years. One day, while being stationed in the northern region of the Norlangarth North empire, she was assigned to find and observe two youngsters who had managed to chop down one of Quinella's indestructible barriers, the demonic tree Gigas Cedar, meant to limit the movement of all Underworld Residents. Charlotte caught up with the two young men on the day that they were preparing to leave Rulid Village and hid herself in the hair of the more careless one of the two.
163 days after being assigned to observe Kirito and Eugeo, Charlotte awoke at night and noticed that Kirito's shirt flipped up due to the wind and exposed his navel. Knowing that this might lead to illness and that the next day would be the day of the Zakkaria Sword Arts Tournament, she decided to interfere and use an Aerial Element to cover the exposed navel. Afterwards, she returned to Kirito's hair where she fell asleep.
The next day, she observed the two young men as they finished their morning work and set off on their journey to Zakkaria. As they arrived at the west gate, one of the guard's horse becomes berserk, endangering everyone next to it. Charlotte nearly interfered with the situation and used a Sacred Arts to protect Kirito, but the young man managed to find what was causing the horse to go out of control and managed to calm the horse down before Charlotte managed to take action herself.
After the incident, she observed the two as they signed up for the tournament, while pondering about their mysterious Aincrad-style and whether the two had any plans to ensure that they would be assigned to different blocks during the tournament, but from a later conversation she realized that the two had not thought things through that far.
At 11:30 in the morning, when the two young swordsmen arrived at the tournament restroom, Charlotte was shocked to hear Kirito warning Eugeo that one of the participants, a seemingly harmless person, might do something. When the time came for the draw, Charlotte realized that Kirito intended to draw first, in hopes of being able to distinguish the colours of the balls while there were many of them left, but such a method would not work in Underworld. Charlotte then decided to intervene again and help the two boys be assigned to different blocks. After ensuring that the two young men drew different coloured balls, Charlotte suddenly remembered the supposedly harmless participant who Kirito was worried about and, being driven by curiosity, she decided to ensure that the mysterious apprentice guard was assigned to the same block as Kirito.
After the preliminaries, Kirito was assigned to fight against the apprentice guard, Egome Zakkalight. During their battle, Charlotte learned that Kirito identified Egome as the one who released the Large Marsh Horsefly on the horse at the west gate earlier that day, which was why Kirito was cautious about him. As the battle intensified, only Kirito's sword appeared to be losing its Life and Charlotte frantically opened the Stacia Windows for the two swords, only to find out that Egome's sword had 1.5 times the priority of Kirito's. After Kirito dodged Egome's blow, causing him to hit the marble wall and suffer the effects of the recoil, Egome decided to end the match by activating his Secret Move, Azure Wind Slash. At that moment, realizing the danger of using such a skill in battle, Charlotte attempted to subconsciously warn Kirito to put down his sword to stop Egome from attacking. She even considered revealing herself to stop the battle, even if it was against her orders, but before she could take action, Kirito activated Snake Bite and easily countered Egome's skill. The shocked Charlotte then realized how much Kirito exceeded her expectations and thought to herself how she would like to see the end of Kirito and Eugeo's journey.
By the 3rd month of 380 HEC, Charlotte had followed the two young swordsmen to the Sword Mastery Academy, where she secretly helped Kirito by pulling his hair whenever he was about to cross the line to secretly warn him. One example of such an instance was when Kirito attempted to try out a 5-hit Secret Move in the Academy's forest, as Charlotte most likely sensed the presence of Uolo Levanteinn, but Kirito ignored this warning and continued with his attempt, staining Uolo's uniform in the process. That evening, after Raios Antinous and Humbert Zizek snapped all of Kirito's Zephyria flowers, Charlotte again interfered, but this time she spoke out to him to told him not to give up and to believe in his own power. She also told him that the other flowers in the garden wished to help him restore his lost flowers and that Sacred Arts were just a way of arranging and guiding thoughts to tap into the power of imagination and that he did not need words to guide the energy of the flowers that wanted to help him. Because of this encouragement, Kirito was able to revive his dying Zephyrias with the help of the four Sacred Flowers in the garden.
Sensing the presence of Eldrie Synthesis Thirty-one in the Central Cathedral's rose garden, Charlotte warned the two escaped prisoners by pulling Kirito's hair. However, before they managed to take action, the Integrity Knight called out to them to come out. They soon engaged in a battle which was interrupted by another knight armed with a bow when the two escapees started reminding Eldrie about his past life. After Kirito and Eugeo started fleeing from the attacking knight and into the Cathedral's garden maze, Charlotte began pulling Kirito's hair left or right whenever they reached a junction in the maze and Kirito immediately took the designated route due to his lack of time to think things through. After the umpteenth junction, they arrived at what seemed to be a dead end, until Cardinal opened one of her backdoors, which was linked with the dead end, and let Kirito and Eugeo enter the Great Library Room.
After Kirito asked Cardinal if she had been spying on him with her familiars as well, she confirmed this and called Charlotte out by reaching out with her hand. Charlotte then jumped out of Kirito's hair and finally showed herself to Kirito. A few minutes later, without answering any of Kirito's doubts, she got off Cardinal's palm and disappeared into a nearby bookshelf, having finally completed her duty as a familiar.
After Quinella summoned the Sword Golem that easily defeated Kirito and Alice, Charlotte, who had secretly continued following them, told Eugeo to stab his dagger into the elevating disk in the floor. While Eugeo was doing so, Charlotte returned to her original size and attacked the golem to buy time. Although she was able to hold out against the golem for some time, Charlotte's front legs began to break. However, Charlotte continued the struggle and attempted to attack the Piety Module that was the golem's weakness, but her other legs was soon severed by the golem. Charlotte then attempted to bite the golem, but before the attack could reach, she was kicked by the golem and lost two more legs. She attempted to get up and attack again, but was pierced by the golem before she could do so. Just then, Eugeo stabbed the dagger into the elevating disc. The spider still attempted to get up, but powerlessly sunk into a puddle of her white blood. She then faced Kirito and told him that she was glad that she could fight with, but her words ceased at that moment as she passed away.
- Charlotte seemed to have developed the method of pulling Kirito's hair to interact with him during the events in Zakkaria, when she pulled Kirito's hair to vent her frustration with his lack of planning. Kirito mistook these warnings as his own divine inspiration.