Located in the deepest part of the Black Iron Palace's underground labyrinth, the safe zone was a remarkably intact square room.
It had only one entrance and was incredibly spacious, devoid of any decorations or furnishings. All that adorned it were white walls, floors, and ceilings. The sole exception was the black cubic stone table placed at the center of the room.
Sitting atop this dark table in the midst of the entirely white room was Yui, wearing a white dress. Her presence in the midst of all that blackness was strikingly apparent.
At this moment, as Yui gazed at Rozen and Asuna lying on the ground, she smiled gently. However, seeing that smile on Yui's face didn't bring any joy to Rozen and Asuna; instead, it weighed heavily on their hearts.
That smile lacked the innocence and purity it used to have; it was now filled with a complex blend of emotions, resembling sadness and melancholy.
Therefore, Rozen and Asuna couldn't find any reason to be happy.
"Gu!"
"Gu!"
In contrast, Saichou and Hanachou, as if completely unaware of the situation, continued to cheer and flew towards Yui, displaying their evident affection.
Observing this, Yui's smile softened with a similar complexity, and she reached out to pat Saichou and Hanachou's heads.
"Thank you for being with me during this time," Yui softly expressed her gratitude.
Her demeanor was quite different from the Yui they knew before. Rozen and Asuna had already risen from the ground.
"Yui-chan..."
Asuna looked at Yui, her expression was shaken and careful as she called out Yui's name.
Rozen, on the other hand, remained silent, his gaze fixed on Yui, not making any move.
Yui redirected her gaze to Rozen and Asuna.
"Mr. Rozen, Miss Asuna."
Her voice remained familiar, but there was a sense of unfamiliarity in her addressing. Rozen refrained from comment, while Asuna seemed to be affected by the addressing, shivering slightly.
Whether Yui noticed this or not, she continued speaking with a somewhat ethereal smile.
"Although I'd really like to ask why both of you are here, but upon careful consideration, it wouldn't be surprising for Mr. Rozen to find his way here."
While Yui's tone had become unfamiliar, when she mentioned Rozen, there was still a genuine sense of joy and pride in her words.
Rozen, unsure if he had noticed this, smiled lightly, feigning ease.
"After all, you seemed a bit unusual tonight, so I thought that if I followed you secretly, maybe I could find out something."
That was Rozen's plan.
"I'm sorry; I didn't mean to leave so suddenly," Yui lowered her head and apologized. "It's just that the automatic repair program had started to take effect and guided me here for adjustments, so I ended up leaving home and coming here, almost like sleepwalking."
Yui's words made it impossible for Rozen and Asuna to ignore the implications.
"Automatic repair?" Asuna was bewildered.
"Program..." Rozen slightly moved his lips, finally converting all his doubts into one crucial question.
"Yui," Rozen stared directly at Yui and asked, one word at a time, "Who are you?"
With the utterance of this question, the atmosphere around them changed significantly.
Yui, as if she had known she would be asked this, gradually let her smile fade from her face.
But Yui didn't choose to remain silent.
"This world - Sword Art Online - is managed by a massive system," Yui began her explanation without any apparent reason.
"It's a system capable of maintaining the balance of this world based on its own judgment, designed with the concept of not requiring human intervention. It has two main programs that cross-check each other's errors and use countless sub-programs to make all adjustments in the world. It's called 'Cardinal.'"
---'Cardinal'.
That is the system that governed this world and it was akin to a set of laws.
"Functions like the AI of monsters and NPCs, the balance of item creation and currency, player attribute enhancements, floor weather and climate changes, and so on, are all operated by program groups under 'Cardinal's' command. It can achieve near perfection without requiring manual adjustments or operations to run the entire world."
Yui explained with a calm tone.
"But there's one task that must be carried out by humans."
What task was that?
"Troubles arising from a player's mental state that can't be resolved by the system; only humans can handle those."
Yui lowered her head, her voice the only thing reaching them.
"However, the developers of 'Cardinal' wanted to assign all tasks related to player well-being to the system. They created a program that could closely monitor players' psychological states using the 'NerveGear' features, visit players with issues, listen to their concerns, and even gave the program emotional emulation capabilities to avoid causing discomfort to the players."
Hearing this, Rozen and Asuna had a certain premonition.
As if she had seen through their thoughts, Yui revealed an empty smile again.
"Originally, this program was supposed to start visiting players on the day the game officially launched, entering its operational phase. However, the main system, 'Cardinal,' suddenly issued an unexpected command, prohibiting her from any interference with players' actions. This left her only able to continue monitoring players' mental states without being allowed any direct contact."
The so-called unexpected command could only have come from the sole game manager of SAO - Kayaba Akihiko. Yui didn't mention him but continued with her explanation.
"I'm sure both of you know what the mental conditions of the players trapped in this game, which later became a death game, were like."
Was there even a need to say it?
"Fear."
"Despair."
"Anger."
"Sorrow."
"Under the sway of various negative emotions, players' mental states became extremely unstable, and some even fell into madness."
Yui bit her lip and spoke softly.
"Watching over these people's hearts continuously, she had a program setting that required her to soothe players' emotions and offered comfort. However, because she couldn't actively engage with players, it created a severe contradiction. The program kept accumulating errors and started to deteriorate gradually."
When she got to this point, Yui lifted her gaze and looked at Rozen, her young and radiant face showing a genuine smile for the first time since she had started explaining.
"Just as her AI program was on the verge of failure, one day, she suddenly noticed a player with a different mental value from the others."
Upon hearing this, Rozen's heart couldn't help but skip a beat.
"That was..."
Asuna seemed to grasp the significance, too, and she looked at Rozen.