A/N: If you weren't reading this when it was first uploaded, this is the author returning after pretty much a year of abandoning this story (2/1/24) to try and continue it. Yep. That's the plan.

PROLOGUE

"Look at the treehouse my dad built us!" The small boy pulled his slightly younger cousin behind him with a grin. "Ta da!" He did jazz hands as he gestured to the treehouse in his backyard. "Mom says we only have like, a few minutes to show you it 'cuz of dinner and stuff."

"It's… nice…" His cousin smiled, her hands folded as she looked around at it, rocking back and forth between her heels and tip toes.

"C'mon, Tessa, you gotta check out the inside so we can decide how to decorate it!" he declared, beginning to climb the ladder to the inside of the treehouse.

"I will follow you, I promise." Tessa had always been a timid girl. Unlike Frisk, she was never riled up and awfully bad at most outdoor games like tag, or basketball, or hide and seek. In that way, the pair at least balanced each other out. Frisk never seemed to mind that she was more into things that required no competition like looking at the wildlife or any plants around. She was his cousin, and she at least treated him like he was a good friend of hers.

At that time, Tessa's parents had recently gone through a divorce, but she still lived about a block away from Frisk with her mother. Although she was bounced back and forth between the homes of both of her parents, she usually visited Frisk while she was with her mom. For another couple years, it would remain that way.

"So, what do you think? I'm thinking a HUGEEEE TV, a popcorn machine, some bean bag chairs…" Frisk began to ramble. Tessa listened, waiting until he was done with his list to give her input.

"I don't think we can have some of that stuff up here, because we won't have the electricity, but I like the idea of bean bag chairs. Maybe some blankets and pillows too, just to get more comfy if we ever fall asleep up here." Tessa clicked her heels as she spoke, wondering what he would make of it.

"Great idea!" Frisk agreed with a toothy grin. "We can keep board games up here, maybe we can paint it-"

"Frisk, Tessa!" his mother called lit from the back door of their house. "It's time for dinner, remember? Finish up what you're doing and get inside!"

"Pssssh. I guess that's our cue." Frisk blew a raspberry at the door when his mom disappeared.

"I guess so," she agreed quietly, making her way down the ladder first, because otherwise they were never going to leave.

Three years passed. The two had made the treehouse their home base, even if Tessa's visits were less frequent. They no longer went to the same school after her mother had moved into a new house with her new stepfather.

"It really has been a few months since we've visited here, hasn't it?" Tessa murmured. At that point, they were both thirteen. They were reaching the end of seventh grade, and Tessa had grown more and more pessimistic, Frisk noticed. Before, it was just shyness. Just a couple words here and there when she felt comfortable. He couldn't remember when he first noted that she seemed more gloomy than usual, but he knew it'd been at least a year since she'd been herself.

"It has been." Frisk flopped down on his beanbag, opening up the book he was reading.

"What's that?" Tessa couldn't help but ask.

"It's a fantasy novel about monsters living in harmony with humans on the surface. One day, a war broke out, and the humans sealed the monsters in a mountain with their magic. It's really cool," Frisk explained, flipping through some of the pages. "At different points, it even sounds real."

"I sure wish it was. I'd rather be down there than up here," she admitted with a sigh, looking out the window longingly.

"Aw, come on," Frisk tried to wave it off, "There's still some great stuff that you'd miss out on Underground. Like rain, and sunlight, and cell service!" His attempts to reassure her seemed in vain. She just shrugged and mumbled a halfhearted agreement.

Come on, Tessa. Work with me.

Tessa was missing.

It'd been three years. The three years must've been hell for her, he figured, if she'd run away from home and wouldn't even come back for her father, whom she had actually cared for. She rarely got to visit over the past three years, but he tried to keep her happy the times she was over.

There was no traces on her disappearance. Absolutely none.

Frisk was worried about Tessa, yes, but grew more concerned when the disappearances began to rise. It was only a week later when the next, but just as mysterious one, happened. A boy around their age, supposedly even a good friend of Tessa's, had gone missing. Then it became a friend of his. And a friend of that friend. By the time the disappearances had halted, it'd been a month since Tessa had seemed to just vanish out of thin air.

After close observation, Frisk connected the dots. Those teens weren't kidnapped. They knew that something had happened to each other, and they'd immediately gone to find each other when they figured out the location of their friend. Still, he couldn't be certain without physical proof.

It didn't take long to find his proof—every piece had fallen into place when he found a book in the desk of one of his former classmates.

Aiden Tringali was the last person to disappear, shortly after his brother, presumably. If it wasn't for the lack of people in the room at the time, Frisk never wouldn't gotten the chance to rummage through his desk. Snooping was definitely not something he was afraid to do, but not to the public eye. He suspected that maybe he would find something, a hint that led to where they'd all gone, and he could go there too.

The book was about Mount Ebott; it was still newly published, only a couple of years old. Inside was a more detailed version of the tale of monsters he'd read as a kid, but it also continued on to discuss how a child had went missing and perhaps had ended up with monsters in their solitude. The novel was labeled as fiction, but…

To the person reading this, this is Tessa Swanson. I think the tale of the Underground is true. And if it isn't, then that was my mistake. I want to find out the truth. Besides, maybe this place is more safe than the world up here…

On the same slip of paper it was written on, the writing had continued in different colors and in different handwriting. The first that followed was in black ink, nearly illegible, but Frisk couldn't tell if the writer was rushing or just had terrible handwriting. Luckily, with his own handwriting being garbage, he could make out all the words.

Ethan Wright here. With Tessa's disappearance, I've decided to go after her. I know she can hold her own, but I also know monsters aren't your average fighters. If anyone can find her and get her home safe, it's me.

…Harmony, Em, if you find this—don't follow me.

The next one that followed was in dark blue pen, seeming to be neat handwriting but unbelievably rushed.

Harmony Beaulieu, was all it read. Followed after were three more entries, the last one in an umber color.

Aiden Tringali. Ain't no way I'm letting my brother get away with this. Whoever's reading this, you're best off putting the book down and walking away. I know everyone may be as good as dead, but it's my responsibility to bring them back. If you can, burn this.

Indeed, these teens had tried to find each other before it was too late. Maybe they were still alive down there. Maybe they were looking for a way out, but they were trapped and no one even knew where they were. All because they had put their whereabouts in a book and no adult had found it.

When Frisk arrived home that night, he wrote his own note and put it on the bed with his findings. His parents would find everything out when they read it, and everyone would know whether or not monsters were real by the time they were back.

At least, that was what he hoped.

"You know, you're taking this whole journey a little fast, aren'tcha?" Frisk was accompanied by a ghost around his age. Her hair was a light brown, and her eyes were red, unlike his. Frisk's eyes were a plain old brown, on the contrary, but he never really minded that.

"I need to find them, Chara," Frisk tried to explain, running his hand through his hair anxiously. "There's no guarantee they're dead. You heard Toriel. She even admitted that she had no clue. They could be alive. I have to find them."

"Still not so sure why you're concerned about those idiots, but I suppose you probably like playing hero," Chara mused. She herself either had no clue if they were dead or knew they were and was great at hiding it.

"It's not about playing hero, it's about finding my cousin." Frisk kicked at the ground as he approached the Waterfall. "I know you hate people, but I hope you understand family. Family cares about each other. And she's basically a sister to me."

"As if I could even remember." Chara's eyes glimmered, but it was hard to tell if it was genuinely sad or not because of her always dead looking expression.

So far, Frisk wasn't happy about the fact that he hadn't found a single one of the other humans. But they had all passed through, it seemed like. At least, that was what he thought Sans was saying.

Chara was both useful and useless at the same time. She made fun of him pretty often, but she was also guiding him through the Underground, even if she didn't even realize she was helping him. He felt like he owed her, at least in some sort of way, because she had assisted him in getting so far through the Underground so fast.

When they reached Hotland, Frisk found a friend in Dr. Alphys. She even gave him a lead on where the others could've been.

"They all headed for Asgore's castle…" Alphys fixed her glasses as she spoke. "M-Maybe he spared them, or they got through, but…" She went quiet for a moment. She sounded like she knew more than she led on. "I-I'm sure you'll find out once you get there."

It'd taken a little over two days to get through the Underground—or, that's what it felt like to him—but Frisk was about to approach the barrier.

And Asgore.

"This is as far as I can go, Frisk," Chara yawned as they got out of the throne room and closer to where Asgore was standing at the barrier, "Magic's unstable here." Chara's body started to glitch.

"What about you? You said I awakened you. When I leave, what will happen to you?" Frisk couldn't help but ask, a bit alarmed at the sudden news.

Chara's voice grew a little more distorted. "Frisk, I'm dead. A ghost. Frankly, I should be staying dead. When you leave? That's it. Game over for me. But I wouldn't worry about it. I don't want to be alive." Before Frisk could even answer, Chara disappeared into a bunch of buttercup petals. He regretted not being able to say "thank you" for what she'd done for him.

There was no turning back. He stepped forward, letting himself come face to face with Asgore.

"What is your name?" the large goat man asked, his back still turned to the teen.

"Frisk. Howdy." He sucked in a breath of fresh air. "I haven't seen the other humans so far. Did they get home?"

He did not reply.

Frisk's heart dropped. "Did they get home?" he repeated, his voice more strained. He knew he wouldn't get the answer he wanted, inevitably.

The king of monsters shook his head. "You are… just like the others…" he grimaced, turning to face Frisk. In his paw was a giant red trident. On his left, four capsules rose. On his right, three did. Six out of seven of them were filled.

Six humans fell. Six died. I'm supposed to be next.

But I can't lose. I need to avenge them. I have to avenge all of them.

Suddenly, Frisk had torn a sharp knife across Asgore's torso, doing a large amount of damage. Asgore was knocked back by the force, but sent an assortment of fireball attacks, astonished that Frisk managed to dodge most of them. The slight burns hurt, but didn't keep him down for long. He was back at Asgore in less than a minute.

The determination of both of them was too great for either of them to be overtaken. They seemed to have reached an impasse as the battle drew on for longer and longer.

Both were panting. Asgore was fighting for the sake of freeing his subjects. Frisk was fighting for the vengeance of the other humans.

Asgore finally fell to one of his knees, using the trident as support while he tried to regain his breath. But while he was slowed, Frisk took the opportunity to strike. He plunged the knife into his chest, and watched as he stuttered and mumbled and turned to dust.

He sank to his knees. What was the point? They died. They all died. He felt sick. Extremely sick. And dizzy. All they wanted to do was save each other, and they died. Just like that. He felt like a monster. He was the one who told Tessa about the Underground when he read that book years ago. Was that where she got the idea? Was he the one truly responsible for the death of six teens?

The next few moments were a blur, but a… menu… appeared before him. It felt like a video game menu.

[RESET?]

A/N: The point of this prologue wasn't to tell a whole story of the Underground and then reset it, so I didn't spend TOO much time on it. The point was just to give more depth to his motivations and how the timeline came to be.

Anyways, thanks for sticking with me, hope you enjoy the rest of Grouptale :3