December 16

Yuki Nagato sat silently in her corner. The temperature this afternoon was lower than normal, and she was almost shivering.

Error. Humanoid Interfaces should not shiver.

The errors were accumulating. They led to unusual impulses. They had first become a matter of serious concern to Nagato during the time loop the previous summer, but they had begun before then. She had assumed before that they were simply random blips that occurred in all programs, and nothing serious. The first time that she had noticed a serious error was during the first SOS Brigade search for unusual phenomena. In the afternoon, she was paired with Kyon. Since they did not expect to find any unusual phenomena, they had simply gone to the library. She had read for several hours. Kyon had suddenly approached her, displaying the external signs of the human emotion typically referred to as "panic". He had apparently just received a call from Haruhi Suzumiya demanding a justification for their absence at the meeting point. The first error was her own impulse to remain in the library, even though her mission was to monitor Suzumiya.

Humanoid Interfaces should not have independent desires, especially if they are potentially detrimental to the mission.

That was the more disconcerting error, as it directly affected her ability to function. Fortunately, Kyon had intervened by obtaining a library card for her, which would allow her to temporarily take books from the library, including the one she had been engrossed in reading. The next error had seemed less problematic at the time. It was an impulse to somehow reciprocate the action which Kyon had performed on her behalf.

Later, she had researched this impulse. She found that it corresponded to a human emotion referred to as "gratitude". For humans, a necessary component of reciprocal altruism, which was itself a mechanism of group cohesion and survival. Normal and necessary for humans.

But she was not a human. And gratitude was dangerous to her mission. It may inhibit or impel actions that might become necessary to the mission in the future. Occasional errors, she knew, were a necessary result of even a limited capacity for imitating humans, which was necessary for her mission. Interfaces with more imitative capacity could also become unstable more easily. This, Nagato reflected, may have been part of the reason why Ryoko Asakura became unstable.

Later errors, related to her interactions with the SOS Brigade members, soon became a matter of greater concern. And rather than resolving themselves, the errors were accumulating.

The door opened, and Kyon entered the room. "Just you, Nagato?" he asked. She just turned her head and blinked. She knew that Kyon understood. She turned her head back to the book she was reading. Kyon's footsteps were audible. Nagato knew that his first action would be to turn on the space heater. Kyon seemed to have very little tolerance for cold, as evidenced by his tendency to sit in front of the space heater, his tendency to wear several layers of clothing in the winter, and his frequent complaints about the cold.

Just then, Haruhi Suzumiya entered the room, throwing the door open and causing it to slam against the wall. This was how she had entered in 97.2% of all entrances to the clubroom. Why did this create an impulse on Nagato's part to engage in mild physical violence?

More errors.

A few minutes later, they were all seated around the table. Haruhi Suzumiya asked, loudly, "Do any of you have plans for Christmas Eve?" An irrelevant question. In the unlikely event that any of them did have alternate plans, Haruhi Suzumiya would force them to set those plans aside.

"I know you don't have any plans, Kyon. " said Haruhi. It is inevitable that he wouldn't. After all, Nagato (and Haruhi, presumably) knew that most of Kyon's spare time was spent here, in the clubroom, or in other brigade activities. "I know you don't have much of a social life, and I only asked so you didn't feel like a loser," Haruhi continued speaking to Kyon. This statement defeated the ostensible purpose for the previous question. Why was the impulse to violence recurring?

Error.

"And what if I did have something going on?" replied Kyon. Haruhi merely responded, "Ha. I knew it." Haruhi Suzumiya seemed to embody perfectly the contradictory nature of humans. Nagato could surmise that Kyon was important to Haruhi Suzumiya, and yet she treated him as if he were unimportant, or even offensive to her, depending on the situation. At least she didn't molest him daily, or wager him as a prize for the computer club…

More Errors. Danger levels.

"Yuki, do you have plans?" "No." She never had plans. Her entire purpose was to observe.

And now Haruhi Suzumiya was removing an assortment of objects from a bag. Yuki surmised, based on their appearance and data that she had absorbed from reading, that these were related to "Christmas".

Haruhi Suzumiya temporarily banished Kyon and Koizumi from the room, indicating that she intended to force Mikuru Asahina to undress. The usual struggle ensued, and Nagato temporarily disabled her auditory input to avoid listening to Asahina's squeals of indignation.

When Nagato looked up, she saw Mikuru Asahina dressed in a red suit with white trim. She was also wearing a strange red cap, and white mittens. Haruhi forced her near the door, announcing, "Okay, you can come in now!" She opened the door and Kyon, who had evidently been leaning against the door, fell backwards into the room and onto his back. Nagato scanned for damage. No serious physical harm.

Haruhi Suzumiya pulled Kyon up by his tie, "How dare you peep at Mikuru's panties, you creep!" "I didn't see anything! Honest!" Kyon responded, sounding panicked. Only partially true. Nagato was aware that Kyon was physically attracted to Mikuru Asahina. It disturbed her that her own reaction to this fact was similar that for responding to threats. Definitely an error.

Nagato filtered out the remainder of the conversation, and returned to reading. Irrelevant data followed, including Haruhi Suzumiya saying something about "sex symbol". A few minutes later, Haruhi Suzumiya dismissed the other members.

Yuki walked, as she had so many times before, to her apartment. She attracted attention from several individuals on the way back, probably due to her lack of weather-appropriate attire. She considered buying some heavier outer garments. Besides ameliorating the physical discomfort from the cold, it would make her less conspicuous at this time of year. The latter could be the justification she used if her behavior resulted in a query from another interface.

But the errors were getting more severe. This shouldn't happen. But apparently even a low-imitative-capacity interface like herself could build up errors this severe.

It was an unfortunate situation, from the Data Integration Thought Entity's point of view, that a human, especially one as emotionally volatile as Haruhi Suzumiya, should have so much power at her disposal. The situation of an individual with human emotions and superhuman powers was not one that the Data Integration Thought Entity wanted to replicate. It was a point driven home by Ryoko Asakura's breakdown and attempted termination of Kyon, which could have destabilized Haruhi Suzumiya.

The Entity would not take that risk in the future. If it found out that Yuki Nagato was accumulating errors to the extent she had, she would either be heavily modified, or deleted. So every day, even as she found herself changing, she maintained her façade, lest one of the other interfaces should find out and report back that Nagato was becoming unstable.

Back at her apartment, Nagato read for several hours from a book she had checked out from the city library. This, at least, she enjoyed, and she was grateful to Kyon for helping her to make a library card.

Error. Error.

And, knowing that, she began to despair.

December 17

After sleeping for several hours, Nagato awoke. Her body required sustenance. She had not eaten in 24.3 hours. She noticed that she had gotten up slightly later this morning than usual. For a human this would not create any significant distress, since she still had plenty of time to prepare and travel to school. But this deviation from her normal schedule was just another reminder that sooner or later the breakdown would come.

She changed into the school uniform she wore every day. She walked the same route that she had walked since April. Every day, it was the exact same number of steps. She had eighteen fewer minutes than usual to read before class, due to her delay in waking up this morning.

Classes passed uneventfully, much as they always did. She went to the clubroom to read during lunch.

After classes, Nagato was the first to the clubroom. She read for 17 minutes before Haruhi Suzumiya entered the room.

The crisis was very close now.

Haruhi Suzumiya wanted to decorate. She asked what sort of food they should have. She couldn't decide on anything other than "not crab". This somehow led to a lecture on why Haruhi Suzumiya believed that crabs should have evolved with no shells, so that they would be easier to eat, apparently ignoring that such a trait would actually be maladaptive.

"Haruhi, I think we're out of tinsel," said Kyon. "Fine, then go buy some yourself," replied Haruhi.

Why didn't Haruhi get it herself, if she was so intent on decorating? It occurred to Nagato that Kyon would probably also be expected to pay for the tinsel out of his own pocket, despite his absolute disinterest in decorating. It occurred to Nagato that Haruhi Suzumiya's tendency to use Kyon as a secondary source of funds for Brigade activities must place a significant financial burden on him, which she understood could be a source of mental stress for humans. Unlike herself, Asahina, and Koizumi, Kyon had very finite resources at his disposal. Was that why she was affected by an impulse to defend Kyon against Suzumiya?

Yet another error. And a dangerous one. If Nagato were to act on it, it would almost certainly destabilize Haruhi Suzumiya. Even if she did not destroy the universe, Nagato herself would almost certainly be recalled by the Data Integration Thought Entity. And she knew what would follow.

If only the world couldn't be destroyed by this human on a whim, Nagato thought. If only the Data Integration Thought Entity hadn't sent her to observe Haruhi Suzumiya.

A few minutes later, Haruhi Suzumiya dismissed the brigade members.

It was so cold. And it was dark, as she walked back to her apartment. The same number of steps she had walked this morning. She went to sleep early. Another deviation from her normal activities.

December 18th

Nagato awoke at 12am. The errors were propagating. This was happening faster than she thought.

There was a way. To be free. Of Haruhi Suzumiya. Of the Data Integration Thought Entity. She could do it with Haruhi Suzumiya's own power.

Error. Danger. Abort thought process.

Irrelevant. This couldn't continue. She didn't know what destructive forces Haruhi Suzumiya might call up in the future. What if Haruhi Suzumiya created another centuries-long time loop?

But was this only her choice to make? For some reason, she thought of Kyon. If course, his memories could be altered, along with everyone else's to accept the alternate world. But something caused her to recoil at the possibility.

But what would happen to Kyon if he kept his memories of the old world, but then found himself thrust into a different one? He would probably reject it at first, but was it unreasonable to think that he might come to accept that world? It would be logical, given his reactions to Haruhi Suzumiya. But if he didn't? Would she condemn him to a life miserably placed into a world that wasn't of his choosing? But then again, he hadn't chosen this world, either.

So he would get a choice: Haruhi's world, or the altered world. If he was really determined to return to this life, it would be possible. I will place an escape program in that world. If this world is what he wants, he can do what is necessary to restore it. As for my memories, there is only one that I wish to keep. I do not want the endless summer, or the cave cricket entity.

But another voice in her mind spoke up. But what if he rejects the world I create? Then the Data Integration Thought Entity would almost certainly have me deleted. That's a threat I can't allow. But she could not bring herself to accept that voice's advice. The nature of the errors in her system was such that it was leading to contradictory actions.

Despite these misgivings, Nagato made her way to the location where she would change the world. The process began.

And then the world changed

"Miss Nagato," said Ryoko Asakura in a concerned voice, "what are you doing out here?" "Wha-?" said Yuki Nagato. She didn't know why she was outside, in her school uniform, at all. She didn't know where she was. And what was Miss Asakura doing here, wherever here was? Yuki did know that it was bitterly cold. Her uniform didn't provide any real protection from the temperature, and she shivered uncontrollably.

"I-I must have been…sleepwalking?" she said, uncertainly. "Come with me, Miss Nagato," replied Asakura, "we need to get you inside as quickly as possible. It's too cold to be out, especially with the virus going around. I happened to see you leaving the apartment building, because I got back late. Your eyes were open, and you seemed to be walking very quickly, as if you had something terribly important to do. I wasn't sure what I should do, so I followed and watched you. It's my fault you came out this far. I should have known that people can seem almost completely awake to others, even when they're sleepwalking."

Internally, Yuki sighed. Good Miss Asakura, always looking out for her. It was still a mystery to the chronically shy bookworm why the popular class representative took such an interest in her welfare. She couldn't stand to see the closest person she had to a friend berate herself so harshly, after she had followed Yuki at this hour out of concern for her safety.

"Don't worry…" she started softly, but trailed off. Asakura produced a jacket, which she gave to Yuki, who accepted it gratefully. Her legs, which were barely covered at all by her uniform, were still cold, but the jacket helped warm her upper body. She couldn't help but wonder why Miss Asakura carried an extra jacket with her, since she apparently only chanced to see Yuki leaving the apartment as she was arriving. But she wasn't about to complain. It just showed how well-prepared her friend was for any situation, Yuki supposed. And she felt tired, so tired, as if she had just performed some Herculean task. She supposed it must be the cold getting to her.

Asakura took her by the hand, enveloping Yuki's small and ice-cold hand in her (only slightly) larger and warmer hand, and led her back to the apartment building at a brisk pace.

Asakura let go of Yuki's hand when they entered the building. Although she couldn't explain why, it relieved Yuki greatly when Asakura let go of her hand. Although she would never admit it, for some indefinable reason she was often uncomfortable around Miss Asakura. It bothered her that she should feel uncomfortable around someone who was always so kind to her, but still she couldn't shake that apprehension…

Yuki was temporarily worried that she may have left her keys when she sleepwalked out of her apartment, but to her relief found them in the same pocket they were always in. Once they were back at Yuki's apartment, Yuki thanked Asakura, and gave her back the jacket Asakura had lent her. "You know, Miss Nagato," said Asakura, "we really need to see that you get some warmer clothes for winter. Maybe we could go to the store this Sunday, and I could see about getting you something heavier." "I'll think about it," said Yuki softly. She really felt that she didn't deserve Miss Asakura's generosity, and didn't like to see the girl going to so much trouble on her account.

"You're sure you're all right, Yuki?" asked Miss Asakura. "I'll be okay," replied Yuki. "You know I could never forgive myself if you got hurt, don't you?" asked Asakura. "I understand," said Yuki, though secretly she thought it was a strange thing for Miss Asakura to say. With another concerned look, Asakura left, closing the door behind her.

After Asakura left, Yuki tucked herself under the kotatsu. She was too tired to bother changing into pajamas, and fell into a dreamless slumber almost immediately.

Author's Note:

Okay, for a prologue that was way too long.

If you've read this far, you've probably noticed that I'm attributing some sort of latent, unconscious knowledge of events in "Melancholy of Haruhi Suzumiya" to the human version of Nagato, even though she's not supposed to have any memories of it. To that, I would simply say:

We don't really know what she remembers, because we don't have a window on her thoughts like we do with Kyon. And Kyon is a fallible narrator, so just because he doesn't notice something doesn't mean it doesn't happen.

As I'll explain in later author's notes, I think having such knowledge floating around somewhere in her pre-conscious mind explains some of Nagato's actions.

We already know that Nagato is fallible too. "I forgot to recreate the glasses" moment and all that. So she may not have completely expunged her own memories. Or maybe it was deliberate. There are reasons to believe that as well, which I'll elaborate on later. And in the Endless Eight everyone except Haruhi appears to have moments of deja vu (and even she may have had such moments as well. Nobody discussed it with her, so we really don't know), so this isn't without precedent in the series. And even if on one level Nagato wanted to get rid of all but one of her memories, on another level she probably would have rejected getting rid of them completely. They are, after all, a part of who she is, and she obviously put some of her old personality into her human version (like an enjoyment of reading, for example).

The point of all this is that it's not unreasonable, within the plot presented in Disappearance, to suggest that the human version of Nagato may have some traces of her old memories. So I think I can justify it as filling in the blank spaces in the plot, rather than rewriting it