I know this is starting to sound old, but sorry for the wait. Exam week, writer's block, not sure how to write Undyne, etc. etc..
Getting acquainted with Frisk proved to be slightly more difficult for Undyne than it was to the Dreemurrs and the skelebros. Aside from being so shy, Frisk appeared to hold some kind of fear for the imposing Royal Guard leader. Initially, Asriel thought that that fear originated from Undyne being a Monster, but this was proven to only be half the truth: the skeleton brothers and even the king himself had earned the child's trust quite a bit quicker.
Asriel eventually concluded that this was because of Undyne's rank in the Royal Guard, her impressive strength or her eyepatch. Maybe it was all three. To his relief, however, the fish woman remained patient with Frisk, and was quick to shrug off the kid's reflexive flinching.
"Don't worry about it," she had grinned when Asriel mentioned it. "Who wouldn't feel threatened when facing me!"
Eventually, Frisk's flinching became less and less as the day went on. When it was time for another slice of pie, Undyne went to talk to Asriel in private as the Human child ate.
"The kid's got a strength," Undyne said. "Heh…she's a total wimp, but she's got a strength."
"You were a bit…freaked out when you came here today," the king said. "There's something wrong, isn't there?"
"Right," the Royal Guard leader responded. "It's actually kind of funny. Y'see, there's been a bit of a panic in Snowdin." She looked him straight in the eye. "Rumors of you walking around with that kid."
Asriel blinked. "Panic? Why?"
"You mean aside from there being a Human in the Underground all of a sudden? Most people have never even seen a Human, and now their king is suddenly walking around with one."
"Right…" the king mumbled. "Maybe I should've told everyone about her."
"Can't say I disagree," Undyne dryly said. "I mean, the kid doesn't really look like a threat, but we all know what Humans are capable of. Child or not, they're scared of her."
"I guess I should've seen this coming," Asriel said. "Oh well. Too late for regrets."
"You mean you're going to announce it?"
"I don't see any other choice. I just hope…" He trailed off.
Undyne narrowed her eye. "You just hope…?"
The king sighed. "How do you think they'll react when I say that I've got a Human in my house? Keeping it silent was a mistake, but they'll still be…"
"…scared of her," the Royal Guard leader realized.
A brief silence fell.
Undyne shrugged. "Well…honestly, I don't think the kid would like it any more than the people. I mean, she doesn't seem like the type of person who'd want to be…feared."
"She's experienced quite a bit of fear herself," Asriel mentioned.
"What do you mean?"
"From what I gathered, her parents weren't the best people in the world."
"Why? What happened?"
The king sighed. He was about to tell Frisk's history to someone again. Sure, he wouldn't do it if he didn't trust Undyne, but he still didn't feel comfortable with it.
"It happened the very first morning after her day of arrival," he eventually said. "She was crying because of a bad dream she had. When I heard it, I went to her room to calm her down – only for her to get even more scared."
"Well, she was new there, wasn't she? She still had to get used to living among Monsters and whatnot."
"That wasn't the reason. You see, she was apparently used to…being punished for crying."
Undyne's eye widened as she started to understand.
"She said that her parents would hurt her whenever she cried," the king continued.
"What!"
"Keep your voice down a bit, will you? She's still right next to us."
"Those parents!" Undyne growled. "Those scum call themselves parents!"
Asriel deeply hoped that Undyne's barely contained rage wouldn't scare the kid in the room right next to them. He kept an eye on the doorway to make sure that Frisk wouldn't be peeking around the corner and see the Royal Guard leader stomping the floor to bits.
"Seriously, why would they even do that?" Undyne raged. "Why would they hurt their own kid like that! If it weren't for that Barrier, I would personally pay a visit to those punks and see if they like being beat up all the time."
"Look, Undyne," Asriel calmly interrupted in an attempt to calm her down. "I agree with you. What Frisk's parents did is unacceptable. But Frisk is here now, and all we can do is make sure that her future will be better than her past. Her parents can't hurt her anymore. Now, she'll have to adjust to the Underground, and the Underground will have to adjust to her. It's our job to make sure that'll go without problems."
Undyne sighed bitterly, but nodded. Asriel understood her anger towards the two Humans that called themselves Frisk's parents, but he knew that, even if he could get to them, trying to get revenge in any way would only make things worse.
Fortunately, there was nothing to indicate that Frisk had heard the conversation between the two Monsters.
"You're right," Undyne eventually sighed, having calmed down a bit. She then got a determined look. "But I won't let them take her. If that Barrier ever falls, there's nothing to stop me from keeping that kid out of those people's house. I'd kick their asses if that's what it'd take."
The king nodded approvingly. "I can live with that."
For her entire life, Frisk believed that Monsters were evil. She used to be scared of them. She used to have nightmares about inhuman creatures creeping out of her closet or hiding under her bed at night. Those were the kind of nightmares that would indirectly cause one of her parents to bust into her room and give her a beating.
But she never dreamed of a benevolent, fuzzy goat man who gave her a place to stay. Nor did she know that Monsters had parents, but Asgore and Toriel were as real and friendly as Asriel himself.
Skeletons did appear in her dreams a few times, but Sans and Papyrus' somewhat amusing behaviors had at least partially deterred her fears when she first saw them. Asriel's reassurance had helped as well. Her shyness was left unaffected, though.
While she couldn't remember having nightmares about fish women, there were some things about Undyne that frightened her. But even she turned out to be nice. She seemed a bit scary and behaved a bit differently from the Dreemurrs and the skeletons, but she was a good person.
This was slightly confusing for the Human child. She had always believed that Humans were good and Monsters were bad. But as she looked back on her experiences, it seemed to be the complete opposite. She had no doubt that there were still good Humans out there, but she was mostly surrounded by the malicious ones. At home and at school.
When her abusive parents told her about how the treatment she received would prove to have a positive effect on her in the future, she didn't expect her future to include eating a delicious pie at the dining table of a lovable, furry Monster king. But she wouldn't want it any other way.
For the first time in her life, she felt safe.
For the first time, she had friends.
For the first time, she had a true guardian.
