Frisk woke up at 2AM the next day. Their insides were gurgling. It felt similar to a grumbling stomach, but Frisk was not hungry. Instead, they just felt nauseous.

Of course, they attempted to fall asleep again. It was far too early for them to get up. Unfortunately, their body had a different idea. A few moments later, Frisk had an acid reflux that they tried to swallow back, but that still managed to leave a bad taste in their mouth. They tried getting rid of it by swallowing their saliva a few times but it didn't have much effect aside from making their mouth dry.

Deciding to try and ignore it anyway, Frisk closed their eyes and rolled around to try and force themself to go back to sleep.

A couple minutes later however , they had a second one worse than the first. It even made the back of their tongue sting a little from its acidity, making the young human frown a bit.

Frisk raised their torso to reach a sitting position, in the hopes that having gravity working against it would prevent it from happening a third time.

It did seem to work to some extent, they stayed like this for a few minutes without another reflux. However, they did feel their head spinning a little and their throat and mouth felt dirty and dry.

Eventually, they decided to get up and drink some water before trying to fall asleep again. They walked slowly as to make sure not to risk waking up Toriel. Luckily for them, the bathroom was located just next to their room. Frisk took a glass and filled it up halfway with cold water before drinking it.

They did feel a little better for a moment, but just when they were about to head back to their room, their nausea doubled in intensity and they felt their diaphragm and their abdomen contract. They only had a couple seconds to react before throwing up in the sink.

They felt disgusting. The taste was terrible, the smell was terrible. And most concerning of all, among the gastric acids and remains of food, were those traces of blood in their vomit ?

Frisk let the water run again, first in order to wash it away, then for rinsing their month and get rid of the taste, hopefully for good this time.

Was this another side effect ? Chara finally spoke up after having remained silent since they woke up.

'Most likely' Frisk thought back to them while checking in the mirror if there were any traces of it on their pajamas. Luckily for the human, there weren't.

We can't continue like this for much longer. The first fallen human commented. Our situation appears to be worsening.

Yes. Frisk knew that very well. But they had already done everything they could do so far, right ? Besides, they would get the MRI results later today, surely they could figure out what to do from there ?

I guess you're right.

When Frisk went back to their room, they opened their window before going back to bed, hoping that having some fresh air would prevent them from getting nauseous again.

They were pleasantly surprised to have managed to fall asleep again so quickly. It felt like it had been less than a minute since they laid on bed again and yet it had been four hours. The quickly got up and proceeded with their morning routine.

They didn't really have anything planned for today, so they could do pretty much whatever they wanted for entertainment. Maybe they could find some board game to play with Toriel ? Maybe call some of their friends ? Or they could just stay on their own and do some nerd things with Chara. To be honest, given their current situation, it was probably going to be that last one. It would get pretty problematic if they ended up throwing up or having another headache intensity spike in front of someone and made them worry.

Well, they guessed there was an argument to be made that they should let people who care about them know how bad things really were, but the cause of these issues was something they could hardly understand or believe, let alone help them with. It was probably better for everyone if they didn't know the full story. Especially according to their companion who had no intention of being exposed.

While the two headmates had a short inner debate regarding wether to drink apple juice or grapefruit juice, a knock was heard on the door.

"Who's there ?" Toriel's voice responded from afar as the boss monster approached.

"aaron"

Oh no.

They hadn't taken this into account. 2 weeks ago on Sunday, just a few days after they reached the surface, Sans had shown up uninvited so try a knock knock joke on Toriel, who then invited him in leading the two to end up chatting and telling each other jokes for some time, which Frisk had even participated in (To be exact, they repeated the jokes that Chara whispered to them.) Then the next week on the same date and time, he had shown up again. As the two of them used to practice jokes to each other in the underground, Frisk guessed that these Sunday mornings were probably going to become their new weekly pun hangout.

They liked Sans, of course ! he was a great friend ! It was just that he had a certain skill for somehow figuring out a lot of things going from very little information. Frisk had learned to not underestimate the skeleton when once upon a timeline, he had managed to find out about their time travel ability simply by noticing that they looked bored repeatedly in situations that should have picked their interest of that they solved some puzzles way too easily for someone who had never seen it before, such as MTT's colored tile maze.

And well, in a situation where they were having to hide a lot of pretty important things, having Sans around did make them a little anxious.

He was never able to pick up on my existence in any previous timeline iteration. Why would he do so now ? Chara asked with very little confidence. It seemed they were more trying to convince themself that it was true than anything else.

Both of them knew that the presence of their friend didn't really have any symptoms in the past aside from when they let Chara control of their body. Now however, the physical and mental changes were very noticeable from the eye of an outsider. They would indeed have to be pretty careful not to let too many signs around him.

"Aaron who ?" Asked Toriel, who had now reached the other side of the door.

"why aaron you opening the door ?" The skeleton delivered his joke.

Toriel let out a quiet laugh before opening the door. Frisk themself was unable to restrain a little giggle.

"hey tori, what's up ?" He asked.

"Oh well, we are still trying to finalise the formalities for living on the surface. For the most part though, things are working out just fine." The former queen explained. "Do you want something to eat, Sans ?" She proposed.

"nah, i already got something." Frisk wasn't looking but they could imagine that it was probably a hot dog. Either that or ketchup.

"heya frisk." Sans called out to them when he saw them. The human hummed and gave a little wave as an answer without looking at him in the eyes.

The two monsters then went to the living room while Frisk want back to their own room as they were not particularly eager to participate this time around. Frisk couldn't understand what they were saying, but as they regularly heard laugh coming from afar, they could assume there were unsurprisingly at least some jokes involved.

Hey, Frisk ?

'Yes ?' The latter responded mentally.

Vomiting blood can hardly be a good thing. Can you search about this online ?

Without more words, Frisk went ahead and did so. There was apparently a medical term for that : "Hematemesis". It was considered a pretty important and concerning sign medically, there were multiple possible causes for it but none of them were very good. Aside from the one involving having previously ingested blood, which Frisk had obviously not. They closed the page before making themself worry even more. This would likely come up with the MRI anyway.

After around an hour, another short knock on their door signaled Sans' arrival. The human tilted their head around to meet the skeleton's eyes as he entered their room.

"kid ? you've been kinda quiet today." He began. "how's life been treating ya ?" The short monster tried to start a conversation.

"Could be better." Frisk answered, remaining quite vague.

Sans looked to the side and sat down next to frisk. "well, lighten up bucko. things never go perfect. instead of thinking about how things could have been, try to make the best of what's given to ya." The skeleton's advice felt like it was more than a simple life tip. He seemed to feel quite strongly about what he had just said.

Quite the ironic words to say to someone with a power like yours. Chara commented from within their mind.

But Frisk did sort of agree. Although what was currently being "given to them" was quite troubling.

"I guess so." They finally responded. The skeleton's grin grew slightly larger upon hearing those words. "What about you ?"

Sans looked to the side. "papyrus is trying to get a driver's license. its... uh... a work in progress. but im sure he'll make it in no time"

Noticing his answer had been about his brother rather than about himself, Frisk playfully reacted. "Hey, i've asked about what's been up with you Sans !"

"okay, sure. but how's about you go first ?" the skeleton asked.

Go first ?

"Go first ?" The human child repeated to the monster.

"i dunno, you still haven't told me anything." Sans pointed out.

Act natural. Chara reminded Frisk when they were about to flash a nervous smile by manually preventing them from doing it and leaving a slim twitch near their jaw as the only trace of what Frisk had been about to do so.

"Me ? Well, i feel a bit sick lately but other than that nothing much." Frisk answered. Sans seemed somewhat unsatisfied with this response. He stared at them blankly for a moment before closing his eyes.

"hmm... that expression." He started, freezing the children in place. "that's the expression of someone who's hiding something" He pinned them with his glare.

'Crap' both of them thought simultaneously. As they got visibly more tense, many of their muscles contracted in reaction. They became conscious the moment it happened that this had most definitely not slipped by the skeleton's body langage detector of a mind, which could grill a hot dog from 5km away.

Sans chuckled. "don't sweat it kid. just remember you've made some good friends. these people really care about you, ya know ?" The skeleton got up and glanced at them with a worried look. he stayed like this for some time before heading back out of the room. "well, see ya."

That went...

"...Well ? But also kinda bad ?" Frisk finished Chara's thought for them. He had certainly seemed to notice they hadn't been telling the full story, but at least he wasn't into what that full story was ? His departing words felt like they were trying to suggest Frisk to tell their friends about what they were hiding rather than keeping it to themself.

They decided to remain in their room until Sans left, just in case they risked giving away anything accidentally. It was the safer bet.

"tori ? can i ask you something ?" The skeleton sounded a bit worried.

"What is it, Sans ?" She responded.

"is there something happening with frisk ? seems like they've been avoiding me today and i get the feeling there's something they aren't telling us." Sans brought up.

"Frisk has not been going very well lately. They are fairly stressed and they've been quite sick. Sweating, having headaches, they've even passed an MRI. Excuse them if they aren't in a very good mood." The boss monster tried to justify Frisk's actions.

"heh, maybe. i still think you should look out for 'em though. still feel like they know something we don't and they don't wanna share it."

Toriel believed she knew Frisk pretty well, and whilst they had certainly been acting a bit oddly, Toriel could difficulty imagine them hiding something of major importance from her. Nevertheless, she noted what Sans had said in a part of her mind before wishing him goodbye and returning to her occupations.

It was only late in the afternoon that she was disturbed again, this time however, it was her phone. She had been messaged by an unknown number. It had sent her several messages along with a few documents. After giving it a quick look, she was fast to identify those as Frisk's MRI scan results. Intrigued, the boss monster decided to take a look.

Oh, god...

"F-Frisk ?" Their adoptive mother's voice trembled as she tried to catch their attention.

"What is it ?" the child wondered.

"The results are here..." Toriel answered.

"Oh ! What do they say ?" Frisk asked.

"...Lets sit down." She requested.

This is not a very good sign...

Toriel brought up her phone and showed Frisk what she had been sent. The first part was mostly administrative formalities, so she skipped straight to the part that mattered. "The way your organs are disposed is slightly atypical." She started. "Many of them are positioned very slightly differently than what one would expect, they should be going back to normal over time, but until then, there are many possible side effects or increased vulnerabilities."

Frisk took Toriel's phone from her and scrolled through the list in search for a few select things. In between loss of balance or stomach aches (Frisk was glad not to have had that one. Headaches were already bad enough), they eventually found nausea and low iron (which would explain the light headedness) among the likelier symptoms and hematemesis among the unlikelier ones. So they guessed that they did have their explanation regarding those. There were a few other concerning things though like a weakened immune system or difficult digestion.

It was pretty insane how a few slightly oddly placed things in there could cause this many issues, at least this was not going to be permanent...

Frisk gave a short nod and gave Toriel her phone back.

The monster's eyes lowered as she selected another document.

"This is the part that is the most concerning." She looked at them worryingly whilst the report regarding their brain opened. This was probably not a good thing. As far as they knew, the anomalies spotted in brains via MRI scans were rarely anything good. Usually it was things like tumors or strokes. After all it could hardly be a good thing to have something wrong with such an important part of their body. What worried them most however was the nature of what exactly could they have "found".

The boss monster remained silent for a moment before showing them some radio images along with some complicated text and the words "Frisk syndrome" written in bold letters. Frisk didn't understand much of what that all meant.

The fact that this wears your name cannot be good either.

"My child, do you know how thoughts work ?" She asked them.

That was an odd question.

'I do not like where this is going.' they both thought at the same time.

Frisk didn't answer.

Toriel decided to give them an oversimplification of a more complex process that would allow Frisk to understand without too much difficulty.

"You have nerves cells which can detect information from the outside world through your senses." She began. "And those cells can transmit this informations to other cells so that all of the cells can talk to each other. They can change, learn, adapt, and coordinate together to create thoughts."

Frisk was getting a bit afraid of what she would say next. Chara remained silent.

"And... Why is that important ?" They dared ask the question.

"Well, Frisk, your brain is doing something strange. Its spending much more energy than it should on its thought process." As she said those words out loud, Toriel realised that this was probably why Frisk had been eating a lot since yesterday, that extra energy they spent had to come from somewhere...

"When it receives information, it shares this information in between its cells too many times. The activity detected in your brain was 1.7 times as intense as it should have been. They think that the initial information might occasionally be shared to networks of cells more than once. Basically, your head is trying to formulate a thought multiple times from the same thing rather than just once. This might be the reason for your headaches." She attempted to remain calm and collected while explaining.

"This is something that has never been seen before. Your case is unique so they do not know how to treat it either. It shouldn't be too dangerous aside from what you've already experienced, but they still want you to come to the hospital very soon just in case. Just to make sure that you're fine and to learn more about your condition. Is this alright with you ?"

When she looked back up at her child, she found them shaking. They looked absolutely mortified. Oh, dear... She had tried to not scare them but it appears Frisk was quite afraid of what she had told them.

Meanwhile, within the child's head, hell was breaking loose.

Nononono. This is not happening. We are going to wake up.

'Chara, please' Frisk tried to think to them. 'Calm down.'

Calm down ? Calm down ? Frisk, you know exactly what this means. It could not be clearer, they know there is more than one set of thoughts forming in your head. This can only be because of me. Do you know what will happen next ? They are going to make you take more tests. They are going to make you a guinea pig to study you and your condition, and then... and then... They will find out about me. And once that happens they wil-

'CHARA, STOP !' Frisk interrupted them. 'Please. Listen'

What is there to listen to, Frisk ? We are screwed. Screwed.

'I know this looks bad, but they don't suspect a separate consciousness. They just think im wasting energy by overproducing thoughts. And even if they do run tests or ask questions or something, i can just... lie to them ? I won't let out your secret as long as you aren't comfortable with it.' Frisk attempted to reassure their friend that although this was not looking good, they were most certainly not doomed either. They just had to stay determined as always.

"Frisk, dear ?" Toriel snapped them both back into reality after watching her child shaking absentmindedly for a concerning amount of time. "Do you hear me ?"

"Oh... Sorry !" They apologised.

'I think i should accept. At best they can help us without knowing it, at worst we will lose some time. We don't have anything to lose by accepting to go there, do we ?' Frisk thought in direction of Chara.

I do not like this. The first human restated.

'I get that. But i really think we'll be just fine. Can you trust me on this ?'

Chara internally sighed. I guess i will. Buy please be careful.

"When would that be ?" Frisk asked.

"The last message suggests you to come to the hospital as soon as they can have a room adapted for a case like yours ready. Which should be in about a day." Toriel answered.

"So... After school tomorrow ?" They asked for confirmation of what they believed to have understood of the planning.

Toriel nodded in response.

Just before she left, the monster turned around one last time to reassure them. "Don't stress yourself too much over this, i am sure everything will turn out fine."