Three years ago, you did the impossible.

Using nothing but raw, unyielding Determination, you stared down a god who begged for death—and you chose mercy anyway.

You shattered the containment barrier that had sealed monsters underground for generations, liberating them to the surface.

Humanity braced for an apocalyptic, all-out war, but your quiet kindness proved them wrong.

Instead of bloodshed, your victory ushered in an unprecedented era of peace, unity,

and shared views between the two long-divided races.

Now, you find yourself walking along a sun-drenched beach, the rhythmic crash of the waves matching the peaceful hum of a world finally at rest.

As you approach the sea, your eyes catch a familiar, unmistakable face standing by the shoreline: Undyne.

The fierce, former Royal Guard captain who once relentlessly hunted you down and tried to end your life is now just another soul enjoying the freedom of the surface.

She hadn't seen you yet.

Your eyes weren't exactly focused on her face, but lower... You were looking down at those worn sandals—dirty and deeply imprinted enough to tell tales for days to come.

But what really caught your attention were her large, sweaty feet. Although coated in sand, her red, clawed nails were adorned with gleaming gold rings.

One sandal dangled precariously off of a single red nail, seeming to beckon you closer.

When you finally raised your gaze and locked eyes with your former pursuer, you weren't met with a magical spear.

Instead, she offered you a genuinely warm smile.

And the voice that followed

"Yo! Punk! I thought that was you!"

Undyne lets out a loud, booming laugh that easily cuts through the sound of the crashing waves, waving you over with an enthusiastic arm gesture.

"Look at this place! Can you believe we actually made it? No more damp caves, no more glowing rocks... just real sun and actual sand!"

She shifts her weight, her loose sandal dangling slightly off her clawed toe as she grins down at you.

"Well, don't just stand there staring at the dirt! Get over here!

Three years of peace on the surface, and not a single soul realizes the ultimate savior of monsterkind is a lie.

When Undyne mysteriously vanished from her beachfront home, the public easily believed the forged notes claiming she had gone on an intense, isolated training retreat.

No one suspects that you dragged her all the way back down into the dark, abandoned depths of Mt. Ebott.

You bypassed the ruins, walked right through the empty caverns, and hauled her straight into the subterranean heat of the Core—locking her inside the deepest, most forgotten wing of Alphys's True Lab.

You were too smart to start a loud, chaotic genocide run on the surface. You knew all about her Determination.

If you tried to kill her out in the open, she would have transformed into a heroic nightmare.

Instead, you neutralized her silently and hooked her directly into the DT Extraction Machine.

Now, the monstrous, skull-shaped machine looms over her, humming with malicious power as its cold metallic tubes and siphons drain her soul essence directly into the Core's power grid.

Bound tightly to the operating chair, Undyne is completely incapacitated, unable to fight back or manifest a single magical spear.

She is stripped down, her large, sweaty feet bound flat against the cold metal grating of the lab floor.

The beach sand from the day you ambushed her still cakes her skin, clinging to her red clawed nails and gold rings, while her worn, dirty sandals sit discarded under the machine’s heavy shadow.

The machine keeps her in a perpetual state of agonizing weakness—just alive enough that she cannot turn to dust, but completely drained so her Determination can never trigger a transformation.

You have turned the Underground’s fiercest protector into a private, endless battery.

The heavy elevator doors hiss open, echoing in the damp, quiet laboratory as you step into the room. You offer her a familiar, innocent smile, but the shadow across your face tells a completely different story.

You remember who is really in control of this machine, right? (=

Three years after the barrier shattered, you and Undyne finally returned to Mt. Ebott for a quiet trip down memory lane.

She thinks this is just a sentimental visit to Waterfall—the place where she once fiercely hunted you down, and the place where your mercy ultimately changed her life.

The cavern is just as beautiful as you remember, filled with the gentle, rhythmic hum of the glowing Echo Flowers and the soft, cool mist of the underground rivers.

As the two of you stop by a ledge overlooking the luminous blue waters, your gaze drifts away from the scenery and down toward her feet.

She is wearing those same worn, dirty sandals—deeply imprinted from years of surface life and coated in a light layer of cavern dust.

Her large, sweaty feet shift against the smooth rock, her fierce red clawed nails glinting with their gold rings. One sandal dangles precariously off a single red nail, lazily swinging over the edge as she relaxes completely in your presence.

When you finally pull your eyes upward, you aren't met with a magical spear.

Instead, she looks down at you with a genuinely warm, nostalgic smile, completely defenseless.

That soft expression doesn’t change even as she notices exactly where your attention has settled. A low, affectionate chuckle rolls out of her as she deliberately flexes her toes, making the dangling sandal slip free with a soft clack against the stone. The bare sole is broad, warm, and faintly damp from the long walk and the cavern’s humidity—calloused from years of training yet still soft through the arch. She plants that bare foot right in front of you, sole upward in open invitation, then draws you closer between her powerful legs.

With the same focused intensity she once brought to battle, Undyne lifts both feet—one still loosely sandaled, one bare—and presses the warm, slightly sweaty soles against you. The weight is solid and confident. She begins a slow, deliberate rhythm, the textured pads and firm arches creating steady friction as she works you between them. Her red claws flex and relax carefully, the gold rings cool against warmer skin, guiding without ever cutting. The dusty, lived-in scent of her feet mixes with the cool mist rising from the luminous waters below.

She keeps moving her strong soles in unhurried strokes, toes curling and uncurling around you, the dangling sandal occasionally brushing your skin with every pass. Her expression stays soft and nostalgic the entire time, completely open, completely defenseless. The pressure builds under the firm, rhythmic squeeze of her feet until you finish between those warm, sweaty soles. Undyne holds you there through it, soles pressed close, toes flexing gently as she works every last bit out, then finally eases her grip with a quiet, satisfied exhale.

She looks down at you still wearing that same warm smile, the glowing Echo Flowers humming softly around the two of you as the luminous blue waters of Waterfall continue to shine below the ledge.

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