Kirito, his brother, has divine objects


Spoiler alert: This article contains marked Details about the future as it is published in the novels or content that appears in a current film adaptation. Don't open the spoilers if you want to be surprised in the anime adaptation.


Personal information

Right name

Avatar name

Nickname (s)

  • Mental Health Counseling Program Prototype 001, code name YUI
  • Private pixie

Personal data



  • Kirito (InGame adoptive father)
  • Asuna (in-game adoptive mother)


  • "Mental Health Counseling Program" (formerly) (SAO)


Voice actor

First appearance

Yui (ユ イ, Yui?), Officially "Yui-MHCP001"(Mental Health Counseling Program 001) is a supporting character in the Sword Art Online series. It is a top-down artificial intelligence (AI) program originally developed by Argus to address the psychological problems of players in Sword Art Online (SAO) However, when Kayaba Akihiko turned Sword Art Online into a death game, the cardinal system banned Yui from interfering in any way with the players, causing her to collapse for being forced to use the mental Monitoring the health of the players without being able to carry out her duties. In this broken state, Asuna and Kirito found her in the woods of the 22nd level of the floating castle Aincrad, mistakenly mistaken for a lost player's child and adopted by the couple. After they each other Had reminded of her real identity in a hidden dungeon on level 1, Yui ignored the orders of the cardinal system and practiced her game Master rights to save Asuna and Kirito from the deadly scythe, which resulted in the system marking them for deletion. Before that could happen, Yui's program files were detached from the system, converted to an in-game object, and stored in Kirigaya Kazutos (Kiritos) NerveGear. After Sword Art Online was deleted, Yui's data and Kirito's account were imported into ALfheim Online, as the game is based on the data on the Sword Art Online servers. In ALfheim Online, Yui is treated as a navigational pixie by the game's system, which gives her access to the game's database. After the Fairy Dance, Yui's data was moved outside of Kazuto's NerveGear, giving her access to devices outside of games.


Sword Art Online

Yui had long, dark hair and bright black eyes, and her standard outfit was a one-piece white dress with a bow tied around her waist. During her time with Kirito and Asuna, she sometimes wore a long-sleeved pink sweater and purple skirt, as well as red shoes (brown boots in the anime).

ALfheim Online

As a navigational pixie, Yui is four inches tall and wears a long, light pink tube top dress with detached sleeves, pink anklets and a blue flower in her hair.


Yui had become melancholy when the death game began, as she was not allowed to comfort players and she was forced to keep monitoring their psychological parameters. When she finally, after almost two years of seeing only madness, misery and anger, noticed a couple expressing happiness and joy, she was overwhelmed by curiosity which led her to ignore the command of the cardinal system, not interact with the players.

When her memory was damaged, Yui's behavior regressed on that of a child. [Citation needed] She cheered when Asuna and Kirito pretended to be her parents, [citation needed] but she also showed signs of persistence, such as a refusal to staying with Sasha when Asuna and Kirito decided to go to a hidden dungeon to rescue Thinker.


Yui was originally created by the developers of the Cardinal System to take care of Sword Art Online players who suffer from severe mental health problems. However, when the game officially launched on November 6, 2022, she was ordered by the cardinal system not to interact with the players. Caught between her instruction to take care of the players' mental health and her inability to interact with them, Yui could only watch the decline in her mental health and gradually collapsed over the mistakes that resulted from that contradiction.

One day, in the middle of her usual surveillance, Yui spotted two players whose mental parameters were significantly different from the norm. Her curiosity was piqued by the joy and peace she observed in the duo, and Yui eventually developed a desire to get closer to them. To do this, Yui manifested himself in physical form at the nearest system console to look for the two.



The girl in the morning dew

On October 30, 2024, while Asuna and Kirito were investigating rumors of a ghost in the woods on the 22nd floor, Yui wandered near the couple. When the two noticed their presence, the young girl watched them in silence for several seconds before collapsing. Concerned for her well-being, Asuna and Kirito took Yui to her home and put her in her bed, where she remained unconscious for the rest of the day.

The next morning, October 31, at 7:50 am, Yui began to hum Asuna's wake-up call while half asleep. After being fully awakened by the couple, she gave them her name but couldn't remember anything else. Since the little girl had difficulty pronouncing their names during breakfast, she was asked to simplify their names. So Yui hesitantly decided to address the two as her parents and was overjoyed when the frightened duo accepted the roles.

After lunch, Yui was asked to look for acquaintances with Asuna and Kirito. To prepare for the trip, Yui followed the couple's instructions and allowed them to change their gear to clothing more appropriate for the time of year. As soon as she was dressed in warmer clothes, she happily accompanied them out of the house.

When the trio arrived in the City of Beginnings, Yui was unable to recognize anything familiar from Teleport Gate Square and fell asleep when Asuna and Kirito carried her to a church where other young lost children lived. When she woke up, the girl put her hand into the room and faintly remembered how she used to be alone in a deep, dark place before she temporarily passed out after an unusual seizure.

During breakfast the next morning on November 1st, the trio received a request from Yulier, deputy commander of the Aincrad Liberation Army, to rescue the leader of the guild Thinker from a hidden dungeon under the Black Iron Palace. When Asuna and Kirito hesitated to help the woman without first verifying the authenticity of the story behind her request, Yui confirmed that Yulier was being honest, even though she wasn't sure why she was so sure.

After refusing to stay with Sasha, the player who oversaw the other children, Yui accompanied Asuna, Kirito, and Yulier on their way through the Hidden Dungeon and cheerfully praised the others as they battled the dungeon's monsters. After two hours of traveling and fighting, they finally reached the safe zone where the Thinker was. However, when Yulier accidentally triggered the appearance of the "Fatal Scythe", the little girl was brought into the safe zone by the woman to be teleported to safety via a crystal, while Asuna and Kirito distracted the boss.

However, when Yui entered the safe zone, she touched the GM command console, disguised as a black stone cube pedestal in the center of the room, and regained her memories. After accessing the system through the terminal, the girl left the safe haven while Thinker and Yulier teleported away and hurried to Asuna and Kirito, who had been incapacitated by the Fatal Scythe. She fended off the boss's attack on her with an automatic shield of immortal objects before defeating him with an Object Eraser, which materialized as a giant flaming greatsword.

Now that she was aware of her identity as AI and knew that it would be deleted because she had disregarded the system's commands, Yui thanked Asuna and Kirito for their care. Just as it disappeared, Kirito used the still active admin access and his computer skills to retrieve and save them as environmental data on his NerveGear and to save their core programming as a tear-crystal-shaped object in the game called "Yui's heart".

Fairy dance

Yui was revived as a navigational pixie in ALfheim Online after Kirito Yuis found data imported from Sword Art Online. Yui led Kirito to the

right places across the country. Yui also provided information, primarily by providing cards stored in the game's database as well as acting as a player detector, and providing advice when needed to help Kirito find Asuna.

Yui and Kirito were finally able to save Asuna from Oberon (Sugou Nobuyuki). During their reunion, Yui returned to her normal body and they hugged together. However, their reunion was interrupted by Oberon. Since Yui was in danger of being erased, she fled the scene. Yui then tried to reunite with Asuna and Kirito, but only succeeded after Oberon had been defeated and Asuna had been logged out.

While Yui was sad that Asuna had already left, she understood why Asuna had to return to the real world. Before Kirito left to meet Asuna

In the real world, Yui informed Kirito that a rather large file had been transferred to his NerveGear's memory. Yui also informed Kirito that no matter what happened to ALO, she would be fine as she existed in Kirito's NerveGear.

Some time later, Yui accompanied Kirito, Asuna and their friends on a new adventure in ALO.

Celeste Fairy

When Yui was called by Kazuto while he was riding his Bianchi racing bike, she appeared on a display in his sunglasses. After enjoying the view of the cherry blossoms through a camera, Yui was asked to help Kazuto navigate and record data. After twenty minutes of riding his bike, Yui noticed a transmission coming from his bike. At his request, Yui connected to the device that was sending the signal and visualized a girl named Cel who was inside. Since Cel only responded to input from a monitor, Yui offered to give her his voice commands. Before Cel was brought back to her Creator, Yui had a chat with her and received some information during their time together.

Extra edition

Yui: "You two can make other people happy if you are with them and help them. From now on please go and help the people in my place. Share your happiness with everyone else."

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Rainbow Bridge

At the end of the quest "Deep Sea Looters", the group of seven consisting of Agil, Asuna, Klein, Kirito, Leafa, Lisbeth and Silica, along with Yui and Pina, were brought back to Alfheim by a whale. After the group disembarked on a beach in the Sylph area, Yui thanked the whale for letting the group ride on his back. Since the group was concerned about the conversation between Leviathan and Kraken and there was no way to check the NPCs' dialogues, Yui replayed their conversation for the group.

Later, Yui was also there when the group tried to reach the other side of the "lightning dragon nest".

Phantom Bullet

Before Kirito steps into Gun Gale Online (GGO), Yui is mentioned in a conversation between Asuna and Kirito about the possibility that she might have a "younger sister" in the future and how great it would be if Yui in the real world could cross over.

Later, during Kirito's final battle with Death Gun, Yui linked the Bullet of Bullets tournament broadcast to the heartbeat monitor on Asuna's cell phone, allowing Asuna and Sister Aki to see what was happening. After seeing Kirito lose the fight with his opponent, Yui told Asuna to hold his hand, which helped Kirito remember the weapon that was still in the holster on his left side.


Yui: "You two can make other people happy if you are with them and help them. From now on please go and help the people in my place. Share your happiness with everyone else."

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Mother's Rosario

Yui: "You two can make other people happy if you are with them and help them. From now on please go and help the people in my place. Share your happiness with everyone else."

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Ceramic Heart

As she wandered through a field in ALfheim Online, Yui wondered about the meaning of love, an emotion she couldn't understand. Ten days earlier she had met a boy in the same place who confessed to her. Thinking that he was trying to capture her, she had told him that she refused to be his. To her surprise, however, she learned that this was not what the boy was trying to do with his confession, claiming that he just wanted to finally speak to her before giving up the game. When Yui came to Asuna to tell her that she was afraid of not understanding the boy's words, she was suggested to ask the boy personally.

However, the boy had already deleted his account, so Yui hacked the game's server and discovered the boy's place of residence. Yui was brought to the house by Asuna through an audio-visual two-way communication probe. There she learned that the boy was a recently deceased elderly man who had played VRMMO games as a hobby in the last years of his life. She also found that the older man had told his adult daughter before he died that he had apparently met his late wife in ALO.

In the present, Yui judged from her experience that the feeling of loss was what it really meant to "love".


Alicization Running

After Kirigaya Kazuto was badly injured by a former Laughing Coffin member Kanamoto Atsushi (Johnny Black) and subsequently abducted by Kikuoka Seijirou, Yuuki Asuna and her friends began to believe that there was no hope of finding Kirito. But Yui convinced her mother not to give up. Just like when Asuna was captured by Sugou, Kirito refused to give up searching and rescuing Asuna. It was enough to restore Asuna's resolve, and with Yui's help, along with Koujiro Rinko (the late Kayaba Akihiko's love interest), Asuna was eventually successful in finding Kirito.

Alicization Exploding

Yui: "You two can make other people happy if you are with them and help them. From now on please go and help the people in my place. Share your happiness with everyone else."

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Alicization Awakening

Yui: "You two can make other people happy if you are with them and help them. From now on please go and help the people in my place. Share your happiness with everyone else."

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Alicization Lasting

Yui: "You two can make other people happy if you are with them and help them. From now on please go and help the people in my place. Share your happiness with everyone else."

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Yui is the first version of the "Mental Health - Counseling Program" from "Sword Art Online". She is a "top-down AI" that controls the mental health of SAO players

should monitor. It is designed to mimic emotions and interact with the SAO players. During the events of SAO, it becomes self-conscious and a fully realized artificial intelligence built from a program on top of an existing computer architecture, which is why it usually appears in programs based on SAO. Top-down AIs can be thought of as a collection of binary.

She later gains access to the real world through a VR (Audiovisual Bidirectional Communication Probe) probe designed and created by Kirigaya Kazuto.

Picture gallery

see: picture gallery


  • Originally, Yui was supposed to oversee the players, as shown in the opening sequence of the Aincrad Arc.
  • Yui is also able to access search engines and computer networks. Your thought processes are extremely effective, with a 95% extraction rate of useful data.
  • Yui thinks that Kirito's most annoying habit is that he takes naps anytime, anywhere, as it tires her too.
  • Yui enjoys communicating with Pina, as the intellect of the familiar is complex in structure.
  • Although Yui would like to have a younger brother or sister so that she has someone to talk to, she also wants to hog her dad and mom
  • Yui is able to reproduce her original body in ALO but only uses it when sleeping with Kirito and Asuna as her pixie body is more comfortable in many ways.
  • Yui is able to hear the other players' alarms.
  • Yui's interest is in breaking firewalls.
  • Yui didn't like Kirito's spiky hair in ALO as it was hard to sit on, so she had him change his hairstyle to his usual hairstyle on June 23, 2025.
  • In the non-canonical game adaptation Hollow Fragment, Yui shows off her sewing skills by making swimwear for herself, Asuna, and Kirito.
  • Yui appears in one of Asuna's victory poses in Dengeki Bunko Fighting Climax, where she runs up to Asuna and hugs her.

Popularity contest questions [2]

The author of Sword Art Online, Kawahara Reki, held a question and answer session about the characters in the third popularity contest (2005). The spoilers go up to volume 9 of the light novel. It is recommended not to read this if you haven't seen the anime until at least episode 14 to avoid heavy spoilers. The questions and answers are unofficially translated.

Q. Aren't you going to fight again, Yui?
A. Unfortunately, I don't have the capacity to take part in combat in ALO at the moment.

Q. Yui-chan, what is your actual storage volume?
A. My primary thought algorithm is about 3 terabytes. The size of my external storage is already beyond my imagination.

Q. Will restoring this toughest fight ...?
A. I am sadly no longer able to use the Object Eraser.

Q. Are you growing (in appearance), Yui?
A. I'm considering punching dad for a new VR body, sooner or later.

Q. Please tell me "something I wish my parents would get out of" ”.
A. I want dad to stop napping everywhere. It bothers me because it makes me sleepy too.

Q. How do you feel when you see your parents doing their usual lovebird behavior, Yiu-chan?
A. I can't stand it.

Q. are you happy?
A. I still fail to grasp the full meaning of happiness. Is it called happiness when all needs are met?

Q. Is there anything that worries you?
A. I have to take care of data integrity all the time[† 1] to monitor. My only option is to compress my primary thought algorithm into backups, but when I think of how to unzip it and activate it, it scares me.

Q. Do you want to stay daddy's and mom's daughter no matter what?
A. Of course.

Q. What are your hobbies?
A. Penetrating firewalls.

Q. Can you easily change the way you look?
A. That would create a problem with my self-awareness, so I can't change anything about my appearance other than my clothes.

Q. Can you use the Audiovisual Bidirectional Communication Probe?
A. Yes, Papa will take me with him when he goes out.

Q. How comfortable was it to sleep on the rocking chair + Kirito + Pina?
A. It was the best feeling ever.

Q. When mom & dad are offline, are you alone in the house in the woods, Yui-chan? Or do you sleep during this time?
A. I mainly collect or sort out data from the network.

Q. If you turned into human, how old would you be based on your intelligence level?
A. I would like to know ... It is not possible to compare my artificial intelligence with that of a human, so ...

Q. Is it possible to talk to you and see your elven form in the real world, Yui? Also, could the real you be loaded onto a mobile device, like a portable computer - no, a portable AI (heh)?
A. Right now, that would be done on a screen. Otherwise: A mobile device that would be able to load my primary thought algorithm does not exist. However, it would be possible to connect it to a computer via a network.

Q. Is everyone treating you well? Aside from your two parents, who do you like? And why?
A. Everyone treats me very well. The conversation partner I enjoy talking to is Pina-san. Your intelligence has a very complex structure, you know?

Q. Would you like a little sister or brother?
A. I would like someone to talk to, but on the other hand, I would like to have mom and dad to myself.

Q. What do you like to eat?
A. I like everything mom does, but these cookies with honey have been my favorite lately.

Q. What would you do if you saw Papa cheating?
A. I will not allow that! I'll fly there and be in his way.

Q. Oh exactly, can you use swordsmanship?
A. In my current situation I am unfortunately unable to equip myself with any weapons, so ... I wish one day I could have a normal player account.

Q. What do you do when you sleep?
A. I allow my thought algorithm to rest, sort itself and store the information of the day in my subroutines.

Q. If you could get into the real world, where would you like to go?
A. I would like to sleep between mom and dad's real bodies. I think this will definitely be really warm.

Q. Can you go to other MOs besides ALO?
A. I can play PC-based MMORPGs, but for other VRMMOs I don't have a physical brain, so I can't use AmuSphere to log in.

Q. Do you have thoughts of love for dad?
A. Love is the most difficult emotion people have to understand, isn't it? If you mean the desire to always be together, then yes.

Q. What do you think of people other than Kirito and Asuna?
A. I think they are all very nice people. However, I have a problem with Lisbeth-chan trying to get me to do her homework.

Q. Is there a sword skill you'd like to try out?
A. It's not a technology, but I miss Object Eraser-chan.

Q. You're not very busy, are you?
A. After I finished searching all the sources on all the networks in existence, I might understand the meaning of "idle". On my current path, however, I can't even work out how many hundreds of years it would take.

Q. You seem able to use search engines, but what is the extent of what you are able to do?
A. I can boast of having an extraction rate of more than 95% of the useful data, eh-hen.

Q. So, you really can't be able to walk around in your old guise?
A. The data is still there, so I can go back to my old form. The elven shape is more comfortable in several ways, however, so I don't use the old shape that often. Only when I sleep with mom and dad.

Q. Does Midori-san know you exist?
A. You mean daddy's mother, or in other words, my grandmother, don't you? I once told dad that I wanted to say hello to her and he said it would be a disaster if I called her "grandmother"; unfortunately I haven't done that yet.

Q. What do you do when you are alone?
A. I surf the net, read books and sleep.

Q. Besides your pixie shape and your normal shape, what other shapes can you imagine?
A. Just this. However, I would like to create a slightly larger body with me soon ...

Q. If you were forced to say it, would you like Kirito or Asuna better?
A. I wouldn't even say this if I was forced to! I like them both exactly the same.

Q. What would you do if Kirito started dating someone other than Asuna?
A. I know people do that sometimes. Still, can children really choose both of their parents?

Q. I'll get straight to the point, who do you like better, dad or mom?
A. I'll get straight to the point, both the same.

Q. Do you really shop for your clothes?
A. There are some that were bought, but more were made by mom.

Q. What kind of clothes do you like?
A. I really do best relax in a white one piece.

Q. What do you think of your completely empty headed dad?
A. I believe he should marry mom asap in the real world.

Q. Would you recognize Leafa as your aunt or something? (haha)
A. My parents' cousin ... is there an official term for this? Let me see ... It seems aunt grade 2nd[† 2] to be. It's getting a little difficult to say ...

Q. Are you a secret from Midori-san?
A. It seems that way so far. I would like to send greetings to her someday.

Q. During SAO, were there people in a strange state of mind apart from Kirito and Co.?
A. There were many similar patterns. However, when dad got together with mom, their values ​​were really outstanding.

Q. Do you have any problems because you are an AI?
A. If the server on which my data is stored crashed ... This fear is always there.

Q. Sword Art Online, ALfheim Online, it doesn't matter which VRMMO it is, but have you ever wanted to participate as a regular player?
A. Sure I do. I would love to swing a sword around and try magic.