Frisk and Toriel were watching the sunset together. They had just exited the underground, so this was Toriel's first time seeing the sun. Just as it went over the horizon, she turned to Frisk. "Well, what do you want to do now, little one?" she asked.
"...I wanna see my dad."
"Ah, I see. I should have known you wanted to go back home. I understand." There was a tone of disappointment in her voice. Over the short time she had known Frisk, they had almost become like her own child, so she was sad to see them go.
"And I want you to see him with me!"
This surprised her. "Frisk, I am not sure that is a good idea... I am a monster after all."
But Frisk wouldn't take no for an answer. They were insistent on Toriel coming with them, and she eventually had to relent.
The walk there was long and tiring. Frisk led her there by memory, and Toriel was surprised by how well they remembered the way home. Eventually, they reached the Frisk's home, and it was definitely not was Toriel was expecting. With broken windows and scraped off paint covering the tiny house, it was anything but clean. Frisk excitedly ran up and knocked on the door, dragging Toriel by the hand. After a few knocks, someone finally answered. He was a very disheveled man, with unkempt hair and old worn clothes. Despite this, he didn't look dangerous or threatening, and had a rather calm expression on his face.
"Who is i-" he began, but lost his train of thought completely when he saw his child. He fell to his knees and embraced Frisk.
"Thank god. I thought I had lost you." he murmured with tears in his eyes. After returning the hug, Frisk told him excitedly "Guess what dad? When I got lost, this nice lady found me!" as they gestured to Toriel.
The happiness of his father was immediately replaced with fear as he gazed upon her. He immediately put Frisk behind him as he told them "Don't worry. I won't let it hurt you." with a glare in his eyes.
Toriel frowned. It was only natural for humans to hate monsters. This was the normal response, but it still hurt her a little. This hadn't been such a good idea after all...
Frisk finally broke the tense silence, telling him "But dad, she's not going to hurt me. In fact, she helped me out a lot! She led me when I got lost, baked me pie, and gave me a place to stay!"
In response to this new information, he stared at her suspiciously for a bit and eventually asked "...What is your name?"
"I am Toriel... Nice to meet you." she awkwardly but kindly replied. She extended her hand, and his cautiously met hers. They shook. Apparently gaining his trust, the man gave a small smile.
"Well do forgive me then. I had no idea you did all that. Would you like to come in for some dinner?"
Toriel was hesitant at first, but when she saw Frisk's excited face, she knew she had no choice. "If you don't mind..."
As Frisk excitedly ran down the hall to the dining room, he continued to speak to her.
"It's not much, but welcome to our home."
He wasn't exaggerating when he said it wasn't much. Most of the furniture was bare-bones and there were no decorations, save for a few pictures of Frisk's family. "I don't mean to be rude but, um... you're a monster, right?"
"Oh! Right. I guess I should tell that story... It is kind of long though, so maybe we should save it for dinner?"
"Right, I understand. Look, I just want to say... thank you for taking care of Frisk for me. It means a lot."
Slightly embarrassed, Toriel replied "It was really no problem! Frisk is a sweet child."
Over dinner, Toriel told the story of her people, and how Frisk had freed them from the underground.
"...And when we got out, they wanted me to see you."
"I see." He said. "That is quite a story. But I believe you. I mean, what choice do I have? I am looking at a real life monster after all!" he joked. After that, they shared some stories with each other. Eventually though the laughter and noise left the table and a gloomy silence filled the air. "Frisk, why don't you go play outside for a bit? I want to talk to Toriel, okay?"
"Okay!" Frisk replied, and ran out the back door.
"Oh no." Toriel thought. "I knew it was too good to be true, that a human would receive us this warmly. He was probably pretending to be nice for Frisk's sake." However, when the man began to speak, she was surprised to find that was not the case at all.
"Toriel, I'm just going to say it. Can you take custody of Frisk?"
That was certainly not what she expected him to say in the least. After a long pause she replied "A-are you sure? Why would you give them up just after they got home?"
"Look, I'm sure it has occurred to you that we aren't the most... financially well off. We haven't been doing so well ever since Frisk's mom... my wife... passed away. They were a little baby when it happened, but I still think it affects them. It hasn't been easy on either of us. I have to work several jobs just to support us, and sometimes it still isn't enough. And Frisk sometimes has to stay here unattended for... quite a while. It's part of the reason they fell into the underground."
"So that's why they called me 'mom' when we met..." she mused to herself.
"Unfortunately, the situation isn't getting better. I owe a lot of money, and this house is on its last legs. I probably won't even own this place anymore by the end of the year." he explained. "I don't want Frisk to go through that. They're smart, as you probably could tell, and they can go places in life... if they get the right upbringing. And I'm in no position to give them the childhood they deserve. So please. Take Frisk."
"What about you?"
"Oh, I'm sure I'll manage somehow." he replied with a weary smile.
"...Alright. I'll make sure that Frisk grows up right. For them, and for you."
"Thank you. I'll arrange the paperwork, and I'll come visit you in a day or so. In the meantime, can I keep Frisk? I want to tell them goodbye."
"Yes of course, I understand. I'll be waiting." Toriel walked outside and found Frisk. She said to them "I have to go now, but I'll be back in a while okay? You be good now."
Frisk responded with a cheerful "I will!" and waved as Toriel walked off. His father called him over.
"So Frisk, I talked to Toriel, and we decided you were going to live with her."
They gave an enthusiastic "Yay!"
"And you'll come visit too, right?"
"About that... I may not be able to see you for a while."
"Why not?"
"Adults have their reasons Frisk."
"I'll miss you dad. I hope you can come visit us soon sometime."
"I hope so too... On the bright side, we still have another day left, so tomorrow I'll go get you some ice cream."
"Ice cream?! We haven't had that in forever!" Frisk shouted in disbelief.
"Yup! And we can go do anything else you want to do too. Tomorrow is your day buddy."
The next day, Frisk and his dad went all over town and did whatever they wanted to do. Their dad could tell they were having fun. Eventually though, the day came to an end, and they went back home. As cheerful as Frisk had acted through the day, his dad could tell that they were crying that night.
Eventually morning came, and so did the time of Frisk's departure. Toriel arrived on the front doorstep, and they all stepped outside.
"Take good care of them, alright?"
"Don't worry, I will." she reassured him.
And with that, the two of them walked off in the direction of Frisk's new home.
