There are a few things that I need to say as an author, so if you don't want to read through them, feel free to scroll past the text in italic to where the story starts.

First of, let me clear things up by saying that in this Undertale fanfiction (or Fandertale, as I like to call it), Frisk TALKS. I know there have been countless fan arts trying to stick with the mute Frisk thing, but that's not what Toby planned out – to create a mute human. You're supposed to become one with the character while playing the game, and giving Frisk their own speech bubbles (or frames, in Undertale's case) would push you into a third person's perspective. So rather than coming up with a brilliant idea about how to make her stay silent, I'm just letting her talk.
Which brings me to another thing – in my head and, therefore, this story, Frisk is a girl. Probably not much of a surprise, I guess, since most fan comics and fan stories I've read make her female as well. Also (minor spoiler until the end of this sentence), I'm a big Frisk & Asriel shipper and I wanted to dedicate this fanfiction to just that – the Asrifrisk ship. And I'm not saying I'm against gay couples, just that I'm more comfortable writing about straight ones. Besides, we already have the royal guards and the SS Alphyne to represent gay Undertale couples, so...
One more thing – I'm going to try to keep this story as realistic as possible. Which means: A) that I'll stick to the original story as much as I can and not create any alternative endings different from the original game (and I'm talking the Pacifist ending, of course – that's the only one where we meet Asriel anyway); and B) that I'll not create any new, unheard of supernatural powers if I can avoid it. Sure, monsters live among humans now, big deal; but other than that, I'll keep it more or less believable.

I hope I didn't bore you with this intro too much. Now, let's get to the story already!

Prologue: Filled With Determination

First, there was a flower.

The flower wasn't very creative, so they called themselves Flowey. Flowey the Flower. Kinda like Donald the Duck, if you think about it. No? Nevermind then.

There was one more thing (of many) that Flowey wasn't capable of: feeling. Flowey lacked the power to feel any kind of complex emotions, whether it be compassion, love, or even hatred. Now if you know what Flowey's done and/or intended to do, you might disagree with the latter – but keep in mind that what they did, they did because of the very simplicity of their mind. It's kill or be killed, that's what Flowey repeatedly told themselves over and over – so, quite naturally, they lived to gain so much power that noone could kill them. Sure, they were a little sarcastic and black-humored along the way, but which crazy villain isn't?

Then, one day, the flower met the child.

The child that would have ended up dead by Flowey's hands (pellets?) had it not been for a certain flame of hope in the darkness. The child that Flowey watched walk through the underground, making dozens of friends along the way like it's no big deal. That was an ability that, on one hand, has proven most lucky for Flowey eventually, but on the other hand, has given them a few confusing thoughts – them, who couldn't quite understand the power of friendship, no matter how hard they tried, if at all.

And when all came to that one moment, the human, merely hanging on to the remnants of their determination to stay alive, spoke the one word that screwed things up for poor Flowey.

„Asriel?"

He tried to fight it, but having gathered countless souls inside his newly reformed body, all of those overflowing with love, kindness and overall goodness – his own soul, who he himself thought long gone, sort of came out of nowhere and pierced his heart like a silver bullet. Asriel turned into a weeping child (both figuratively and literally), being reminded of all the cruelties he's done ever since he became a flower, and, even worse, being able to comprehend them all. He suddenly knew that he couldn't keep all the souls to himself, torn from the people to whom they rightfuly belonged. In an act of a selfless sacrifice, he abandoned them all, letting monsters finally leave underground for a vision of uncertain, but promising future among the humans.

He then laid down in his beloved field of yellow flowers, waiting to turn back into one of them, and thinking things. He thought that monsters were weird. All of them living their own individual lives, little or big, happy or sad – yet united in a few matters. They all wanted to go back to the surface at last – and now, they could. And they...

...they all cared about Frisk very much.

That was a thing that just couldn't leave Asriel's mind. He had felt the souls of a hundred monsters saying that name in unison – and even now that they were all gone, he couldn't quite forget what a feeling that was. Frisk, Frisk, Frisk, that was all he could think. The human who he had taken so much from, who he tried to hurt repeatedly in so many bad ways – and who, in the end, had forgiven him for everything. Just like that.

Maybe Frisk was right. As a flower, Asriel was soulless – heck, it wasn't even Asriel in the first place. Perhaps he neither should feel guilty for everything that Flowey was responsible for – but rather make sure that never happens again.

As he thought this, Asriel realised one peculiar thing. He still hasn't turned into a flower. He could've sworn he's been lying here, among the blooming buttercups, for days, but his fate seemed to be avoiding him for some reason. He looked at his arm and thought that he might want to lift it – and the arm calmly rose from the yellowness of the ground.

Asriel stood up, confused, but filled with the will to live and love, to find Frisk and be with her once again, as well as with other monsters. Filled with desire to not let himself, or any flower version of him, lay harm on anyone ever again.

Filled with determination.