After completing the music puzzle, progress through Waterfall went a little bit quicker; their travel over the exposed to docks was, fortunately, bypassed with the help of a parallel version of Ned, soaking in the water as always despite the fact that his attitude was a lot grumpier and he was red instead of purple. That grumpy attitude didn't stop them; all Frisk had to do was swing their pan menacingly and Ned carried them both to the opposite dock.
Sans really didn't approve of the way this child made the other monsters cower, but he also wasn't exactly in a position to criticize. It was a pretty good shortcut, anyway, when he couldn't risk making his own. Waterfall was much more bearable than the icy cold Snowdin, that was for sure, but it still was an uncomfortable place, too dark at times and too bright at others.
At the same time, though, it was such a nostalgic trip. Shortly after arriving on the opposite dock, Sans saw the room with a piece of cheese lying half-eaten by a mouse hole and a half-wilted echo flower, almost as he remembered from back home.
Cramped, hopeless sights, but nostalgic all the same.
While he'd been hesitating over that piece of cheese, Frisk pushed him out of the room and said there was 'something that they had to do.'
"what's that?" He had asked.
The question achieved nothing but getting him shoved out of the room even faster, as they said, "Get off my back!" And that was the end of that.
At any rate, it didn't take them long to catch up with him. They continued on for a little while longer, over black platforms surrounded by sickly glowing water and echo flowers that whined as they passed. They had also passed through the cavern that, as he recalled, used to hold Onion-san. Shortly before they entered, Frisk banged their pan against the ground three times; the octopus monster did not appear.
At the other end, in the next room, the child finally said abruptly, "I'm tired. I'm gonna nap."
He had pretended to nap a few times already, but this was something Sans could actually get behind. "right behind you, kiddo."
It was startling how quickly they fell asleep while curled up on the stone floor. But then, they must be used to sleeping on hard surfaces by now. Poor kid. Sans yawned and did the same, propping himself up against one of the walls. Soon he too was snoring.
But eventually, predictably, he had his sleep disturbed some time later.
It was faint, but Sans could hear the distinct plinking of piano keys further on in the corridor, with the child nowhere in sight. Feeling queasy, Sans shuffled down the cavern to another room, one with an old piano on the right-hand side and the open door in the center of the opposite wall. Above the piano, someone had scratched arrows into the stone.
Meanwhile on the piano, Frisk was playing along on the keys, head bent in concentration. The melody was one he was unfamiliar with. They might have just been goofing around, making a cacophony of notes.
But he felt a little better, all the same. "i didn't know you play, kid."
They looked up, startled, and then away again with red rising on their face. They continue to play, halting and broken notes going on as if Sans had not come in at all. So he approached until he was standing right next to piano, listening with half lidded eyesockets. While he listened the child mumbled, without looking up, "only know three songs, though."
"three songs? that's a lot to me, i don't know any." Frisk didn't reply, so he continued, "can i hear?"
The playing stopped. They looked back over at Sans and then bit their lip. He wasn't sure if he had done something wrong, but a moment before he could ask, the kid started to play again. It was a different song-or, rather, it was an actual song at all-one with a slow and repetitive pattern. He could swear he'd heard it a long time ago, in the back of his recollection. On reflection, he realized with a tap of his fingers that it was the song played by the music box behind the statue in his world, and probably in this one as well. Memory.
No wonder the door here was already open.
Frisk played the song for about a minute and then stopped. They said, under their breath, "One." Then they played anew, and Sans didn't recognize the next song. It was faster, a little cheerier, although something somber still rang through in a simple notes that Frisk laid played. They didn't look at him while they played it.
The ground unearthed next to him and, to Sans' surprise, Flowey had sprouted up next to him. It figured that that thing was following them both, or maybe he had been there the whole time. Certainly Frisk didn't react, continuing to play despite the additional audience member.
But Sans raised his brow at the flower, and the flower stuck out his tongue and winked as he said, by way of explanation, "I heard playing."
"amazing what you can hear when you're under the ground like that," Sans mused, and Flowey chuckled nervously. The little plant didn't reply, instead choosing to sway to the piano.
"You should tell him the title of this one," he added.
"No." Frisk growled.
"i didn't know it had a title," Sans said, as if prompting. The child only glared at them, face reddening again, before returning their focus to the task at hand. "this song about anyone?"
"No," was all they said back.
But Flowey was quick to chime in, "It's about me!" Although at that, the music cut off in an abrupt crash of keys.
By now Frisk's face almost look like a tomato, and Sans could only fight laughing at the sight. He turned back to Flowey, "that's cool. they write it for you?"
"I think so!" The flower bounced. "It's called 'Your Best Friend'!"
Frisk did not say anything, except for "Two," in a little, gritted-teeth growl.
But, "it's cute," Sans said. "i like it."
Out of the corner of his eye, as he kept careful watch over Flowey's jubilant expression, Sans could see the child starting to smile through their blush. For him, it was an immense relief. They were finally starting to act like a normal person. "what's the third one?" He asked finally.
Flowey looked up in wonder, "Golly, you can play three now?"
"Mm," Frisk placed their hands over the piano and hesitated, still keeping their eyes averted. Then they constructed with the worn keys a rapid and soft melody, like a fluttering heartbeat. It was definitely different from the first two. "Fallen Down," they mumbled.
But they only played for a moment before a sour key ring out and they stopped, punctuating their misstep with, "Shit!"
Sans and Flowey both remained quiet while Frisk tried again, and again a few seconds passed before another false key was struck. "Shit! Shit!" They paused. They poised their fingers, ignoring the audience, and tried a third time.
For a second it looked like the third time was the charm. The song went on for a little longer, and Sans could almost make out the child humming something along with it. But by the third iteration of the pattern, Frisk hit a wrong note and slammed their hands down on the piano, "Shit!" And then, setting off several notes at once, they put their head down.
"Uh oh. Play time's over," said Flowey, shortly before he disappeared back into the ground.
The whole thing would have been funny if not for the fact that Frisk wasn't moving from their spot and Sans was getting just a little bit anxious that they had maybe started crying. He placed a hand on the piano, trying to spot any heaving breath or shaking "uh, don't worry about it kiddo," he said. "you still play a lot better than me."
Unexpectedly they raised their head at that, although it was only a little. Their hair flopped again, and they squinted at him before relaxing; luckily, he saw no tears in their eyes. Although he thought he saw something... else... on their face. "Hey, are you sure you're actually a Sans from another world?"
He blinked at the question. "pretty sure, why d'you ask?"
Now the child ran a finger along a piano key in vain distraction. "Just... Sans, my Sans, mentioned having a cousin once or twice. I was just thinking, maybe you're him and you're playing a prank on me."
A face appeared in his mind and he banished it. "nah, i'm no one's cousin anymore."
"Oh." They preoccupied themselves now with pressing down on the same key, repeatedly and slowly. "Okay." It was quiet, save for that repetitive note, until the child followed that up with, "Is there a Frisk in your world too?"
It was easy enough question to answer, but he had a suspicion that what he said was more important than this Frisk was letting on. "eh? my frisk?" He had been trying not to think about them this whole time. Considering that they were so far away right now. "yeah. they're... uh, definitely a thing."
"What are they like?" They asked.
A single bead of sweat dripped off his skull. "what're they like? uh, why d'you ask, kid?"
Like it usually went, he had to wait for the answer from this one. "Mm." They slid off the piano stool, apparently done playing, and continued until back in the adjacent room. He shuffled after them as they went on from their; the hall ahead in their journey he remembered clearly, the "rain tunnel" as he liked to call it. There was no bin full of umbrellas, but the prospect of getting soaked didn't seem to bother the kid that much.
They marched through a puddle of water, dauntlessly, before he heard them speak again, "If you're like this... in that world, I must be different too."
"oh, yeah, uh, i think you could say that everybody is different. me, papyrus definitely, that flowey, you..." Sans flinched as the water dropped down from above, striking him on the skull just a little too hard. His other self's coat was to some extent waterproof, but he knew he was going to get soaked a bad headache anyway. His bones were already shaking.
"Uh huh," said Frisk. For a moment that was all. They took out a spider donut, swiped from Papyrus' pantry, and ate it noisily in the rain before continuing, "So how are they different? Are they all... ...?"
"retarded?" Sans offered.
"... Yeah," Frisk snapped, turning back for a second to sneer at him as they moved forward through the manufactured rain. "Are they all retards like you?"
If he had cheeks made of flesh, Sans would have sucked them in. But since he didn't, he just shivered harder instead. "i guess by your standards, you might say something like that. they're all pretty good people, though, my frisk included. although i guess you two are kinda similar. they just don't curse like a sailor is all. they do a lot less monster beating, too." The child flinched up ahead of him and then Sans flinched back, like a reflex. "... uh... y'know what kid, i'm gonna meet you up ahead."
He made an estimation of where to end up next, remembering the spot where the "rain tunnel" ended in his world. He disappeared to that room before he could even hear this Frisk protest. Although he swore he could see them racing and splashing over the puddles, just before his eyes left the room, as if they somehow believed that they would be able to beat him to his destination. It was a foolish thought. When he reappeared in another cavern, surrounded by reeds, he appeared alone.
While he waited for Frisk Sans coughed and shook, trying to shudder off some of his wetness. Despite the dim lighting of the new room and his own faint dizziness, he recognized it well; behind him, there was a jagged break in the rock wall that opened up to a much larger cavern, one with houses, mazes, and traps sprawled about a mile below. Far beyond the sprawling was the familiar sight of a large castle looming large in the distance.
The castle was also sharper and vaguely more terrifying than in his memory, the spires a dark pointed red and the stone covered in cracks. That was Asgore's home, but who knew what the Asgore of this world was like. Rather than linger on that, he studied the glowing "stars" instead. They were dim and also that nauseating green.
Maybe it was better if he just didn't look at anything. So Sans closed his eyes, sighing.
A noise startled him out of his melancholy, moments later.
The kid had made it over, stepping into the room soaked to the skin; they weren't looking at him, and their hands were behind their back. In a quiet murmur, they said, "I'm sorry I called you a retard."
"what."
The two stared at each other, but it was out of the corner of their eyes. The minute twitches of their expression would have gone unnoticed for other monsters, but for Sans it was all the difference between the Frisk that he had just seen in the rain tunnel and the one facing him right now. A downturned mouth, but with downturned eyes and lids that threatened to squeeze tears. He couldn't say that he had seen that coming. If he had, he might've been a bit more considerate and just put up with the falling water.
Oh, well, no way to undo it now.
Frisk just stood in place, speaking in a low voice, "If I stop calling you a retard, will you stop appearing and vanishing so quickly? Wigs me out."
"all right," said Sans. If he could, he would milk that phrase for what it was worth and disappear slowly. But that kind of cheating wasn't possible. So while Frisk crossed over the distance between them he just said, with his grin, "it's a deal."
"Good." The child shifted uncomfortably and started walking; as before, he had no choice but to trudge along after them. "... He did that a lot too. Especially at first. Like fucking Batman."
"like who?"
Frisk's head, at least from what he could see looking at the back of it, dipped down at the query. There was no reply, except a little exhalation that told him nothing. It must be a human thing. The Frisk back home always loved to explain human things to him and Papyrus, but he could understand if this one got tired of it. Trapped underground and away from humans for so long, there weren't an awful lot of visual aids for them to use.
Feeling a brief pain, he wondered if it would be better or worse here to try and change the subject. Eventually, and studying their body posture closely, Sans said in a not-entirely-telligible voice, "hey, eh..." They turned their head, and what he saw of their expression was neutral, so he kept going, "you didn't tell me what that song's about. the one you played on the piano. what did you call it, 'fallen down'?"
Facing forward again, Frisk swung their arms back and forth. "I... 'm... it's... about stuff."
He snorted. "'bout stuff?"
"Yeah."
"what kinda stuff?"
"Well I," they stopped, started, looked back and then faced forward. "I heard it sometimes." There was a loud snort. "I don't really know what it means. Okay? You happy now?"
No, he was not happy... Not that he was unhappy, at least about this. He coughed. "that's fine. not everything has to mean somethin'."
Repeating their own snort, Frisk stretched their arms behind their head and said, "That's right. I don't know why you even gotta ask in the first place." Each time they spoke, their words got quieter and quieter while the sentence went on, "It's a dumb song anyway, jeeze Louise..."
"actually, my name is sans."
"I fucking knowwwww that already," they said, and he couldn't help but laugh. He was encouraged too by the fact that when he did, he could hear them laugh just a little bit too.
The pained feeling relaxed in his chest, and Sans exhaled as he and his bones relaxed with it.
Author's Note: I wonder how many other people headcanon that the music of the game is something Frisk hears in their head. It's kind of corny, but I like it since Frisk can sing and play piano, so they'd have an outlet for it.
Next Chapter: Like Yourself
