I just finished watching SAO, and I'm not sure if this is ever explained:

Yui is a program that supports the psychological health of the players. She states that, for some reason, Cardinal did not permit her to relate with the players, and was limited to observing them.

Why did Cardinal block Yui? Is this explained in the novel perhaps?

If Kayaba created SAO, I'd guess that he also made Cardinal and Yui. I doubt that he'd want to block his own creation from doing its job, so I guess that the fault is entirely Cardinal's.

4 Answers 4


I just searched for the part in the novels - It's the third part of the second novel. But I'm sorry to disappoint you, there's not much explained:

(Source: Baka-Tsuki)

"Although I am unaware of the complete details of what exactly happened as well, Cardinal handed down an unplanned order to me. A complete prohibition from interfering with all players[...]"

Asuna reacted reflexively; she guessed that "unplanned order" was due to the manipulation done by the only GM of SAO, Kayaba Akihiko.

I guess it was developed by many people who planned to add this feature but Kayaba just decided to disable her without letting the other developers know.

  • Yeah, of course, it couldn't have been created by one person only.
    – Saturn
    Mar 15, 2014 at 0:13

I don't think Kayaba worked on SAO alone. This is never explicitly stated. It's likely he had a large part in it, and created most of the core, and designed most of the elements of the game, but I can't see one guy creating everything alone.

Yui was possibly created by someone else who worked on the game (Or possibly even Cardinal). SAO was the first real VR Game, so the effects of being inside a VR world for long periods of time weren't really known. The Cardinal System was created with the intention of being self-managing, so that humans were never needed, to manage to game, or even to update/patch the game. A program to take care of a player's mental health (to possibly avoid law-suits?) was probably part of the plan for that.

Here's a link to a translation of a sort of "Q&A" that the author had with fans, and characters of the story, back in 2005 (when SAO was still a web-novel.)

Q. Did you know about Yui’s existence?
A. I didn’t spare it any attention at all, a great opportunity gone by.

From that, you can infer that Kayaba himself didn't create Yui.


She was there to support players and keep their psych in top condition. The moment the game kept people inside, Kayaba most likely forced her to stop for his "sick game of death".

After regaining her memories, she tells her in-game parents that she had become melancholic when the death game began, as she wasn't allowed to comfort players and was forced to continue monitoring their psychological parameters, but, after nearly 2 years of only seeing insanity, misery and anger, she finally noticed a couple that showed happiness and joy and wanted to be close to the two to experience their emotions, even though she was not allowed to interact with players.

  • 1
    But if Kayaba made the whole death game, why even bother on creating Yui in the first place, if he's not even going to use her?
    – Saturn
    Feb 4, 2014 at 16:55
  • @Omega Monitoring, seeing how the people their psych responds to this. Will people go mad or stay sane ? quiet allot of potential reasons.
    – Dimitri mx
    Feb 4, 2014 at 16:56
  • But Kayaba gave her the ability to "simulate feelings" so that players would like her. Therefore Kayaba did pretend to use Yui to relate with players. Observing players was part of the job, yes, but she also had a feature to interact with people that was supposed to be used (otherwise why implement such feature?) - but Cardinal blocked her for some reason.
    – Saturn
    Feb 7, 2014 at 4:21
  • 1
    It's probable that Yui was created as part of beta testing, to watch over player health - that's the reason everyone was put into their "real" bodies (swapping genders, at minimum). Kayaba certainly didn't do all the work himself, and his company would have included lawyers and doctors (especially the latter if this was the first dive game). In real-world MMOs, developers have a multitude of tools to handle player issues, including finding them before they're reported (when possible) - like the audit program Yui mentions when Kirito logs into ALO. Mar 6, 2014 at 13:35

Another option, are, even if all system are programmed by one or multiple persons, Yui are here as a part of Cardinal System, and The Seed. All the system are programmed not only for SAO, it's ready for creating more worlds (end of ALO words of Kayaba).

It's the same as the link between The Seed created games. These system are present on SAO too (probably), but, you cannot view it because there isn't more games, or, these system are explicit disabled.

Another option are, Cardinal disabled Yui itself, because Yui have GM privileges and can logout players if they're in too bad mod (something stupid in a game without logout button).

  • end of ALO words of Kayaba Are you quoting this from the novel? Or is it an interpretation of the purpose of The Seed?
    – nhahtdh
    Feb 11, 2015 at 20:23
  • On Anime series, when Kayaba gives The Seed to kirito, he tolds "this can create many different worlds" (I cannot view it now, it's as i remember). Feb 12, 2015 at 10:11
  • This was my guess too (that such an AI would have those kinds of privileges), but you probably need to back it up. Feb 12, 2015 at 11:15

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