Disclaimer: I do not own Undertale.
This takes place after a Neutral Run.
It was a beautiful day outside. The sky was a clear, cloudless blue, with the golden sun shining brightly over the landscape. The grass and trees rustled with animals. A squirrel poked its head out from a tree branch, scanning its surroundings.
A mountain, carved out of purplish gray stone, rose in the background of the forest it loomed over. It casted a shadow on the leaves, a silent and sturdy guardian.
All was quiet.
The serene mood was broken by a low rumbling. The squirrel, which had come out of from the safety of the branches to look for food, scampered back to its tree in terror. The mountain shuddered slightly. A brief flash of light illuminated the surrounding area, and the mountain trembled one last time.
The light dimmed, and nothing else was seen.
Suddenly, a small shape stumbled out of the mountain. It staggered into the forest, swaying from one foot to the other. It collapsed onto the grass.
It got up, clutching something to its chest. It looked down and slowly opened its hands.
A small but fierce glow spills through its fingers. The glow softened for a moment, and a heart-shaped object could be seen in the figures hands. The heart pulsed once, and the light that surrounded it began to diminish.
The figure holding the heart gasped and put its hands to its face, trying to stop the light from disappearing. The heart's brilliance faded away completely, and all that was left was the white heart. It looked very vulnerable, as if the glow somehow protected it.
The heart shivers. The figure shivers along with it.
The heart, no bigger than a large diamond but infinitely more precious, shattered without so much as a whisper.
The figure stared at it empty hands for a while. It puts them back on its chest, shoulders hitching with hushed sobs. It then takes off through the forest, tears streaming down its dusty cheeks, tracing silvery patterns of water in the air.
It doesn't look back.
The area returns to its quiet state. Leaves rustled in the gentle breeze. Birds chirp.
Eventually, the sun goes down.
Night covered the sky like a dark blanket of stars. The diurnal animals go to sleep, and the nocturnal ones come out.
Silence.
The sun comes up. It goes down.
Days pass. Quite possibly weeks. Months, maybe?
Flowers bloom, and wither. Animals come and go. Trees grow and die, a cycle of life.
The sun comes out once more.
As the day passed, it started to sink lower and lower in the sky, ready to leave.
Its dying light bathed the forest in shades of orange and yellow. It spilled through the trees, until a ray fell upon an object in the grass.
A cell phone.
Miraculously, it began to ring. Once, twice, three times.
But no one was there to pick it up.
The phone finally stopped ringing. A beep sounded from it, indicating there was a message. The phone auto played it, and a voice came from the device.
"Heya. Is anyone there?"
The voice waits for a second.
"Well, I'll just leave a message…
"So, it's been a while. Since you left, things have...gotten interesting. With Asgore gone, the people looked to Undyne to rule...but she was nowhere to be found. So Mettaton just kind of...took over?"
The voice then lowered to a whisper.
"He's brainwashed everyone with his stupid TV show. And made the into his personal paradise. It's honestly...kinda disturbing."
The voice goes back to its normal volume.
"As for me? Oh yeah...I'm his agent."
There was a rustling sound as the phone was passed to another person. The second person, presumably Mettaton, spoke up, sounding much more enthusiastic than the first speaker.
"Hey there, darling! Thank you so much for your hard work. Thanks to you, the Underground is more exciting than ever!"
Mettaton's tone became dreamy.
"Ooh la la...statues, monuments to my beauty...flowers in the arrangement of my name...hedges in the shape of my smile…
"Under my rule, the Underground's problems are over, baby! Crowding? Dreariness? Who needs the sun when you've got the spotlight!? Economic collapse? Education problems? What!? Everything's covered in golden glitter! There are no problems, beautiful!
"And, I've instated a new policy on humanity. If a human falls down here...they can join my fan club for free!
"Oh, you might be wondering about Alphys. Don't worry! I built a statue of her, too."
Mettaton hesitated. When he talked again, he sounded subdued.
"Really though. I realized I was...not the greatest to her. So I went to apologize. And, to ask her to help me rule."
A pause.
"But I couldn't find her. Trust me, I looked."
Another pause. Mettaton spoke up again, but this time, his happiness sounded...slightly forced.
"Anyway, I hope your life after meeting me...has been worth living. It must be a struggle. Please, think of me always. Just constantly. Think of me posing. Beautifully.
"Oh yessss!"
He stopped, and another person could be heard in the background.
"Oh, my other agent wants to talk."
The phone was passed over again. A loud yell came from it, causing a few birds to flutter from tree branches.
"Hey! It's me, Papyrus! Imagine me wearing cool glasses, and a suit. And imagine Sans wearing sunglasses being a bouncer. That's our life...it's so cool! Things have gotten way better since you came here!"
Papyrus's voice became skeptical. It sounded like he was frowning.
"Well, minus the fact that everything sucks...for anyone that doesn't worship Mettaton. And minus the fact that my friend Undyne is missing. Who knows where she went."
His voice got sorrowful.
"I miss her a lot sometimes."
But he brightened up quickly.
"If you see her, can you tell her I said hi? Thanks! See you later!"
The phone made a clicking noise, and it fell silent once more.
And it stayed silent for many more days to come.