Going Under

She was standing on the edge, clad in her glorious knight armour, peering down at Waterfall. This was her home and she was ready to do anything to protect it. The soft rustling of the seagrass behind her alerted her to an unknown presence.

Undyne turned around and stared at the small silent silhouette that had become something of an obsession for her during the last few weeks.


She prepared to throw herself at the enemy, but then seemed to change her mind and get a grip on her emotions.

‘First, however, as is customary for those who make it this far, I shall tell you the tragic tale of our people. It all started long ago…’

‘NO! You know what? Why should I even bother telling you this?! When you’re about to DIIEEEEE!!!’ She leapt forward, thrusting her spear at the childlike creature. One direct hit to the heart and soon this mockery would be over.

He avoided her spear attacks with ease, going into green SOUL mode. No matter how hard she tried, he was always one step ahead, leading her on into strange patterns that always evaded her charges.

‘YOU LITTLE SHIT!’ cried Undyne, intensifying her relentless assault. Despite her best efforts not a single attack landed, and to add insult to injury, the little monster seemed to examine her in between dodges. ‘How dare he?’, the fish woman thought angrily. She had never witnessed such  arrogance from a human.

Just when she was about to launch a new spectrum of attacks, her arch enemy looked at her, shrugged, turned around and left. Undyne was furious.

‘HOW DARE YOU RUN AWAY FROM ME!!’ she yelled, chasing after him. Still silent, the little devil ran ahead of her, crossing the purple paths and circumventing the blue lakes of Waterfall. It took her a while, but Undyne finally managed to catch up to him and blocked his escape with a timed spear that would’ve pierced him in half if he hadn’t stopped.

‘There you are! Prepare to meet your doom!’

‘Let’s not fight.’ said Frisk, speaking to her for the first time.

‘Not fight? NOT FIGHT?!’ exploded the knight. ‘You’ve been running around causing all sorts of trouble, mocking everyone, and now all you say is “let’s not fight? I’ll teach you your proper place, brat!’

‘Your attacks are weak.’ added Frisk, calmly dodging her spears.

‘WEAK?!?! NGGGRRR’ raged Undyne, unleashing a new volley of front and side attacks. Somehow that wretched creature was always faster than her, blocking, dodging, rolling away from her deadly spear.

‘Weak’ repeated Frisk and set off again, leaving Undyne panting and out of her skin with anger. She followed him again, the physical exertion starting to take its toll, her berserk attacks draining more energy than she was willing to admit. As if that wasn’t enough, they had ran a long distance, approaching dangerously to Hotland. Her heavy armour not helping the matter either, Undyne was feeling more and more frustrated with her inability to finish the fight quickly.

‘Not fight, go back’ addressed her Frisk, with his usual infuriatingly calm voice. Was he not tired at all? Had he not been running his ass off and struggling to avoid all of her attacks?

‘I’LL GEET YOOUU!!!’ yelled Undyne, doubling her efforts despite the warning signs. The chase continued for some time after and the scenery started to change, the blue seagrass turning a greyish yellow as the temperature increased and the occasional lakes turned into hot springs. Taking heavy breaths with increasing difficulty, Undyne struggled to keep up with her nimble adversary. At last, when the ground turned a dry orange and the hot air burned her lungs, Undyne’s head began to spin, her steps became uncertain, the heavy armour weighing her down like a mountain of metal, and she collapsed on the ground, almost unconscious.

Everything was starting to go dark and blurry, when suddenly her helmet was removed and she found a big glass of fresh water right in front of her.

‘Waat---’ she began, her mouth too dry to speak, her body unable to move.

‘It’s okay being weak, Undyne’, Frisk said, holding her head with one hand and bringing the glass to her lips with the other. She went red with humiliation but didn’t have the strength to refuse. Her dignity trampled, she took long, cold gulps and emptied the glass in seconds. Her head cleared a bit, but her body was still cooking in the heat under the armour.

‘Yeah, I’ll take care of that’ offered Frisk, as if reading her thoughts. He grabbed her spear and climbed on top of her, prying open the various metal pieces until he cracked open her metal shell, letting in the fresh air of salvation.

How can he be so damn strong?, asked herself Undyne, speechless in front of the human with childish appearance that had someway completely and utterly outdone her in every possible way. Always being one of the strongest, the taste of defeat was new to Undyne and she found herself surprisingly admiring her enemy.

‘Victors should get a reward, don’t you think?’ asked Frisk, spear still in hand.

‘What…. what do you want?’ she managed.

‘I want you’ - he ran a hand down her scaly body - ‘to repent!’

‘What..?’ Before she could say more, the little demon was on top of her, taking advantage of how unprotected her body was underneath the metal armor. Despite the bulky form of the metal suit, Undyne was actually surprisingly slender, barely filling half the width of her costume. Small as he was, Frisk was easily able to sit on top of her, one leg on each side. He pushed her head down in ground and the fishwoman felt a mouthful of orange dust.

‘You are weak’ he said simply, his hand reaching down to a place where her scales were small and delicate, almost non-existent, and his fingers could easily penetrate her folds. ‘You are weak’, he insisted, pushing deeper inside her and sending her entire body into burning humiliation.

‘No! What are you doing?’ she groaned, but he didn’t pay her any attention and carried on until the wetness between her legs became overwhelmingly apparent for both of them and her groans were but moaning in disguise.

Then he stopped and pulled out, and for a moment Undyne thought that the whole ordeal was over, until there was the sound of something unzipping and she felt the tip of something press against her entrance. Suddenly Frisk grabbed her buttcheeks with both hands and spread them apart and then a long, hard, dick sank deep into Undyne.

‘Aaah!’ she screamed, completely taken by surprise by the size of the thing. She had expected Frisk to be small and thin, but she couldn’t have been farther from the truth. The stories in Alphys’ books were true - humans did wield swords larger than themselves! Her slim physique wasn’t meant for such a large thing, but the creature on top of her didn’t seem to care, pounding her deeper and deeper until Undyne could feel her stomach on the other side being pushed against the metal armor.

‘Remember that you’re weak’ said Frisk again and Undyne could feel a part of her let go and just allow herself to be fucked by this strange creature. Could he truly be that much more powerful than her? Was he someone able to… subdue her? If before there was a grain of resistance left in the once powerful warrior woman it was gone now, and she lewdly raised her ass and accepted her punishment for having been defeated.

A few days later, Undyne was at her home, and while still marked by her humiliating defeat against Frisk, she had mostly returned to her old self again. ‘Let’s bake some cookies, YEAH!!’ she thought, energetically beating the dough and swirling around the kitchen like a hurricane.

Suddenly there was a knock on the door, followed by a hesitant voice: ‘Um… Un-Undyne?’

‘Yeah I’m HERE!’ she shouted back.

‘Wo-would it be alright if I came in?’ the voice inquired.

The fishwoman rushed to the door and flung it open, peering down at the chubby yellow reptilian in a dotted dress, and sighed.

‘Alphys, you don’t need to do this every time, you can just let yourself in.’

‘B-but this is your h-home Undyne-sama…’ the lizard blushed.

‘Oh for GOD’S SAKE!’ Undyne picked her up, gave her a passionate smooch and catapulted her towards the kitchen, where Alphys successfully landed on one of the big fluffy armchairs that Undyne had installed for this reason. The host then returned to her baking, while her guest fidgeted in the chair, throwing her thinly disguised love eyes.

‘So, um, Undyne, how was your day?’

‘It was pretty good, mostly training with the Royal Guard’

‘Really? What did you do?’

‘Oh, the usual stuff, started with a bit of a warm up by lifting Greater Dog 500 times, then did a couple of races with Doggo and then a bit of fighting with Papyrus.’

‘D-did you win?’

‘Yeah, the dude’s a skeleton, I mean no offence, but he doesn’t hit hard at all.’

Alphys’ eyes were shining with admiration. ‘And you did all that in day?’

‘Sure, buttercups, what’s the big deal?’ Not waiting for her girlfriend to actually reply, she continued: Anyways, cookies ARE DONE!!’ She slammed shut the oven. ‘Let’s do something else! What do you want to do?’

‘Ah, um….’ the short lizard fidgeted again, gathering courage. ‘Perhaps we could … watch…. some anime?’

‘Sounds great! Let’s GO!! We’ll watch ALL the anime!’

They moved to Undyne’s living room, sitting at the fluffy couch in front of the TV. Despite there being space for at least four people, Alphys somehow managed to take most of it and end up nuzzled against the flamboyant fish.

Soon enough the screen lit up with giant robots and armies clashing together accompanied with screams like “All hail Britannia!’ and ‘For the Rebellion!’ followed by giant melees and explosions.’

‘WOW! Human history can be so incredible! How did they even build those robots?! I WANT ONE!!’ yelled Undyne, cheering whenever one came up on the screen, regardless of which side it was on.

‘Yes, human… history… can sure be amazing... hehe’ agreed her girlfriend.

Humans. Her last encounter with one had been indeed… exceptional. Undyne’s cheeks still burned whenever she thought of the heated memories. Alphys’ books were right, some humans truly had extraordinary superpowers that even monsters couldn’t compete with.  The fishwoman knew she was pretty strong herself, in fact one of the strongest around the Underworld, yet still she had lost so easily… could there be other humans who’d make a fool out of her in the future?

Lost in her thoughts, Undyne realised she hadn’t been fully paying attention the last couple of episodes and now there was a pink princess shooting people at a stadium and she didn’t know why. More importantly, Alphys seemed to have picked up on her lack of attention and was looking worried.

‘Um… you know… if it’s not interesting we could always…. watch, um, something else?’

‘I was just distracted by how good you were looking tonight’ winked at her Undyne.

‘Oh…’ - Alphys blushed - ‘you don’t mean that’ - she waved her hand trying to hide her face with it.

‘Oh but I do, sweetie.’ Undyne’s head eclipsed the screen as she sat on top of Alphys, pushing her back with a long, strong, passionate kiss that seemed to keep on going, taking her breath away as the warrior played mercilessly with her tongue.

‘Oh… wow… I…’ managed the chubby girl when she was finally released, only to be silenced by her moans as Undyne’s hand reached underneath the dotted skirt and began caressing her.

‘Spread your legs for me sweetheart… that’s a good lizard.’ Her fingers slipped inside her underwear, plunging deeply and without warning, making poor Alphys turn a deep red and struggle to stifle her lewd gasps, too embarrassed to speak. The Undyne was on her again, suffocating her with kisses.

‘That’s a good girl’ she felicitated her lover when she was done, patting her playfully on the head as if she were some kind of pet. She didn’t seem to mind. ‘Now remove your underwear and go lie on the floor.’


‘Yes WHAT?’ snapped Undyne at her.

‘Y-yes m-mistress.’

‘That’s more like it!’ she slapped her on the chubby ass while the lizard was awkwardly getting into the ordered position. As soon as she was done Undyne jumped behind her, lifting her skirt up and ordering her not to look away from the TV while the fishlady set to work pleasing her lover in every possible way into blissful euphoria.

She proceeded to have fun with Alphys that evening, bossing her around, teasing her, tieing her up and, ultimately, bringing her to multiple shattering orgasms as the chubby lizard let herself be used any and every way her violent mistress desired. It was only in the small hours of the night, with her girlfriend fast asleep beside her, that Undyne’s mind drifted back to Frisk and her unfortunate encounter. Was victory meaningful if it was over the weak? She could do whatever she wanted to Alphys, but then again Alphys never tried to resist. And she would certainly never try to do anything to Undyne. No one ever did. No one except Frisk.

It took her several days to find him again, as the monstrous child seemed to be running all over the place and no one was ever able to stop him. They finally met, ironically enough, in the Hotlab again, one day after Undyne had come to visit Alphys at work only to find out she was at an important meeting with Asgore and would not be available. On her way out she heard a weird noise in one of the rooms, where she found Frisk toying with the equipment.

‘YOU AGAIN! Do you need to put your nose in everyone’s business?!’

‘Oh, hello fish.’ The short devil replied, not even bothering to turn around. Did she mean so little to him? A threat so negligent he could turn her back on her? Undyne flared with rage and threw a spear at him, but Frisk just stepped away, letting it shatter the vials behind him.

‘I see you still have an attitude problem’ he observed, poking the end of the spear.

‘FUCK YOU!’ yelled Undyne, throwing a number of rapid spear attacks at him. Frisk rolled out of their way unharmed. The Lab was half in shambled, but the fishwoman didn’t care. She got her next weapon ready, aimed carefully, jumped… and fell flat on her face when the child spilled one of the vials at her feet, making her slip.On the ground, Undyne cried with fury, ready to bit his face off.

‘Don’t’ he said simply, the cold metal edge of a spear suddenly at her throat. ‘What are you doing here?’

‘WHAT AM I DOING HERE?! How dare you?! Alphys works…’ - he slapped her as with the back of the spear interrupting her. ‘Again. What are you doing here?’


The wooden end of a spear was suddenly at her backside and Undyne shivered, regretting her habit of not wearing any underwear.

‘Talk, fishie.’


He dipped the wooden end in a pool of green liquid that was forming on the ground from the shattered vials and pushed at her backside again, this time much more successfully. The viscous liquid served as a good lubricant and with horror Undyne felt her ass stretch as the shaft penetrated her.

‘Talk, fishie.’

‘I was just here to see Alphys, alright?’

The shaft sank deeper and Undyne groaned as the pressure at her bowels made breathing uncomfortable. It was so deep now she could see her stomach bulging on the other end as Frisk continued to violate her.

‘I was looking for you!!’ she finally cried out.

‘Oh, interesting.’ The shaft retracted a bit and was now playing at her entrance, going in and out, then in again, loosening her O-ring. Undyne wanted to die from humiliation.



‘Why were you looking for me?’

‘Because’ -’ she realised it was hard to concentrate with him constantly teasing her ass - ‘because you defeated me..’

‘And? The truth, fishie.’ The spear plunged again and to her great terror Undyne heard herself moan as it devastated her ass.

‘And because I’m weak!!’ she finally wailed in between panting breaths.

‘Finally. I’ll see you around, fishie.’ And with that Frisk left, leaving her alone amidst the broken lab.

In the following weeks the Hotlab incident slowly transitioned into a trend, as Undyne accidentally bumped into Frisk at various locations around the underworld. She wasn’t doing it on purpose, at least that’s what she believed, but somehow she managed to find the little monster wherever she went, and their confrontations always ended in humiliation for the fishwoman.

The first time she saw him after Hotlab was at the MTT resort, a place where Undyne had gone to catch a break and do some gambling in the casino. She caught a glimpse of Frisk loitering around the place and chased him to a dimly lit backroom, where he used his usual trickery to outmanoeuvre her and ended up bending her over a broken billiard table. When he was through with her he even had the nerve to push a few of the balls inside Undyne, making her do the most awkward and humiliating walk home, where she finally managed to get them out in privacy.

Another time was at the garbage dump, where Undyne was having a date with Alphys, when her girlfriend suddenly got an urgent call from Asgore, asking her to report to the lab. After she send her off, the fish warrior lingered at the garbage dump for a while, until she heard rumbling noises coming from a pile of junk not so far away from her. Upon investigation, she found it was the little devil again, doing god knows what with various cogs, wires and pieces of scrap. Undyne jumped in attack, showering him with a volley of spears. Did she believe she had any chances of winning? Why did she persist? She didn’t know. She spent that night stuck head first between pieces of rubble, while Frisk trained her ass with various things he found in the garbage. The torture lasted for hours, getting her panting and moaning, until her inquisitor decided to get in on the action himself and fucked her silly, bringing her to a shameful orgasm.

Undyne continued to fight Frisk on sight whenever they met, but her determination seemed broken. Each time their clash would last a bit less, become a little more meek, half-hearted, artificial. She was no longer hoping to win.

A month had gone without any trace of the devil child, and Undyne had began to think he had finally wandered off somewhere far away, leaving her alone for good. She tried, with moderate success, to get back to her normal routine and forget all about what had happened. She subjected Alphys to rougher and rougher play, a means to override the past experience and replace it with a fresh one. Their new rituals were merciless and intense, involving more ropes than ever, handcuffs, gags, whips, and various other toys. The lizard was ecstatic.

This evening they were quietly watching anime on the TV, Undyne sitting relaxed on the sofa, Alphys on the floor in front of her, bound with a leash and collar and happily eating out her lover. From time to time the fish lady would give her an affectionate slap or pull, an occasional wet kiss, biting her lips, then putting her back to work.

‘Wait here, chubby, I’ll be right back’, said Undyne, tenderly shoving a dildo in Alphys as she placed her in a position where she could see the screen while waiting. She got a little happy squeal in return and patted her on the head before heading to the kitchen to get something to drink.

She entered without bothering to turn on the lights, walking straight to the fridge. The beers she’d left there earlier to cool down were on the bottom shelf, but when she bent to get them, she noticed one of them was missing.

‘Hey fishie’ came a familiar voice from behind. She turned around ready to fling something at Frisk, but stopped herself short. Alphys would hear the noise.

‘What are you doing here you little shit?!’ she whispered aggressively.

‘Still bad manners, huh? And I thought you would’ve learned by now.’

‘Get the fuck out of my house!!’

‘Not before I teach you some manners. Get on the floor.’

‘You’re out of your mind if you think I’ll ever do that, you little punk!’

‘If you don’t, we’ll fight, I’ll win, again, and then your friend over there is going to have a different kind of entertainment to watch.’

‘Why you…’ Undyne drew her breath.

‘Floor. Now.’

She swallowed the insults coming to her mouth and reluctantly obeyed, cursing the wretched creature.

‘I see you’re already all wet down there.’

‘That’s because Alphys was just-’

‘Silence, fishie.’ Without warning he shoved his thick member all the way inside her. Undyne had to clasp her mouth to stifle the moan. ‘Do you know why you love it so much, fishie? Why you keep coming back?’ She couldn’t reply, her hands still tightly shutting her mouth to prevent any sound as Frisk was mercilessly pounding her.

 ‘Because you’re weak. Everyone around you thinks that you’re strong, but you’re not. You’re desperate for someone else to take control.’ He pulled out of her pussy and placed the tip of his cock over her anus, slowly pushing it forward. After all the training she’d received at her night at the garbage dump, Undyne took it easily and not without pleasure as the long shaft penetrated deep inside her.

‘Now you do it, fishie. Show me what you’ve got.’

‘What do you want???’ she hissed back, trying to sound angry despite her arousal.

‘You heard me. Move your ass, show me you mean it!’

Frisk stopped his movements and remained motionless, while still pinning her down to the floor. Very slowly Undyne began moving her hips, first pulling away until he was almost out of her, then pushing back towards him, inch by inch as her O-ring stretched around him.

‘All the way fishie.’ he commanded. She groaned but obeyed,  pushing farther still, her slender body virtually impaled on him, until finally she felt his balls press against her cheeks.

‘Good. Keep going.’ She gasped, a mixture of arousal and frustration, and repeated the process all over again, finding it easier the second time around. Then followed a third, a fourth, and a fifth, each a little faster, a little easier, a little more steamy as Undyne found it more and more difficult to hide her moans.

‘Now call your girlfriend’ the boy commanded, abruptly sticking the phone to her ear.

‘A-are you insane….? She can’t even answer, she’s tied…’

‘I’m sure she’ll find a way.’

The phone rang for a while, but soon enough Alphys’ voice came from the other side:

‘M-mistress?’ Giggles. ‘Why are you calling me from the kitchen, is this a game?’

‘Listen up, chubby!! Have you been good?? Do I need to spank you?’ She tried to sound as tough as possible.

‘Oh I’ve been very good, mistress!’ - More giggles. The lizard lowered her voice - ‘I’ve got it still inside me… but you can spank me whenever you like, hehe…’

‘Quite the façade you’re putting on, for someone who loves being rammed in the ass’ whispered Frisk in her ear, too low to be heard over the phone. ‘Go on, pretend to be strong.’

Undyne struggled to keep her act. ‘Stay where you are, chubby, when I get back you’re going to squeal!’

‘Hihihi’ came Alphys’ laughter.

‘You’re the one who’s going to squeal.’ whispered Frisk. ‘Because you’re weak.’ He was inside her pussy again and the fish warrior realized how painfully close she was to giving in to an orgasm. ‘You’re weak and pathetic. And you love this.’

The burning sensation was so intense Undyne could hardly restrain herself.

‘Go on, tell her what you’re going to do to her.’ Frisk insisted. ‘Whatever you say to her, I’ll do to you.’

‘Alphys…’ - Undyne swallowed - ‘Alphys when I come I’m going to fuck your brains out, I’ll make you cry like a little baby, I’ll make you admit what a weak little slut you are before destroying all of your holes with whatever I find laying around.’

‘Ooooooh!! I’ll be waiting mistress!!!’

‘Yeah… just wait there a little while longer… I’m coming…’ she hung up.

‘Good choice.’ Frisk grinned in the darkness behind her. ‘Now let’s see, what do we have at hand’ - he looked in the fridge ‘carrots, cucumbers, bottles of beer?’

Undyne blushed in humiliation as he spread her ass cheeks. It was going to be a long night.