It was slightly challenging to get Papyrus to agree to set up the duel, but eventually, he conceded. Frisk had impressed the skeleton with his skill in battle, and while he didn't think the human could beat Undyne, he thought they might impress the woman enough to not capture them.
Frisk didn't think that was likely, but Papyrus was still in denial about what capturing the human actually meant.
So, after Papyrus left to give his daily report to Undyne and set up the duel, Frisk was left to his own devices. He decided to do whatever possible to give him the advantage in the fight, which basically meant gathering anything that could be useful.
While waiting for his magic to recharge, the human walked around Snowden and gathered the most useful items. Using the money Toriel had given him, Frisk bought the Manly Bandana and some healing items from the shop. Doing last-minute magic practice probably wouldn't help, so he decided to return to the skeletons' home and meditate while waiting for Undyne's response.
Right now, Frisk was trying to improve his control over his Aura. Whether or not it was the same power from the show he used to watch, he was sure there was more to it than defense. It didn't seem likely, but if it could be improved to the point where he could manifest a semblance, that might-
The door to the house slammed open and in came Papyrus.
"U-Undyne has accepted your challenge!" The younger skeleton brother called out, it seemed like he had run all the way back from Waterfall. "She said the fight will take place tomorrow, at noon, but agrees to meet at the border between Snowden and Waterfall."
That was good news. Frisk had tried pushing the fight a bit later, but she had at least agreed on the location. By challenging her to a duel, he got to have some control over where they would fight. Undyne was too proud to insist they fight on her favored terrain, and her changing the time was probably just to fit in with her concept of a duel better.
Now, there were only final preparations left to get done.
During the night, Frisk once again snuck out of the house, though he wasn't carrying anything this time. Quickly, he retraced his steps through Waterfall and back to the glowing mushroom puzzle. Finally, he reached into the nearby tall grass and grabbed the ballet shoes.
The human needed every advantage possible, and the gravity kick these shoes allowed was helpful in the last fight.
Eventually, he made it back to the house and tried to sleep on the couch. Unfortunately, the tension of the upcoming duel made it difficult to truly rest. Frisk fell asleep late into the night, his mind reviewing strategies to use in the coming battle.
—
It was time.
Frisk had crawled off the couch late but fully rested after his late night. Now, he was once again getting ready to fight the strongest opponent he had ever faced. Flowey was more terrifying but obviously weaker. Sans was trickier, but Frisk couldn't say he actually fought the relatively passive skeleton.
Undyne was pure strength incarnate. The way she used her INTEGRITY magic to fluctuate the weight of her armor gave the guardswomen incredible speed, strength, and durability. She might not have used too many magic attacks during their previous fight, but each one was done with precision and great skill.
"When I said to get a better plan, I didn't mean for you to abandon any strategy at all." Frisk was only slightly surprised by the lazy skeleton's voice. "A duel's not the greatest strategy if you're still weaker than her," Sans stated in a relaxed tone.
Frisk stopped rummaging through his bag and looked back at Sans, sitting casually on the couch and, more specifically, one of the human's extra sweaters. It was just like a sleepover; they hadn't given him a blanket to sleep with, so he had to get his own.
Rolling his eyes, Frisk shooed the skeleton off the piece of clothing; he was in the middle of packing, after all.
"She might be stronger than me, but that doesn't mean I lose automatically. I've taken away her terrain advantage while still having more information on her abilities." He pointed out more to reassure himself than Sans. "But that doesn't mean I plan to win this fight with just violence," Frisk smirked at the now confused skeleton.
"Dare I ask what you're planning?"
Frisk shook his head. "Aren't you going to be watching with Papyrus?" The younger skeleton had insisted on being there. "I wouldn't want to spoil the surprise." Plus, it was kind of embarrassing to say out loud.
After leaving with a chuckle and wave, Sans went to go get Papyrus from his guard duty post. While he was doing that, Frisk got everything ready and started toward the battleground. He was psyching himself up the entire walk for what was to come.
Their battle would take place on the border of Snowden and Waterfall, where the snowy terrain transitioned into the rocky floors of the underground cave. There was the river Frisk had to be careful about. It ran along the left side of the path to Waterfall and would be fairly close to their duel. His best bet was to use his range to kite the fishlike monster away from the water. The plan was to draw her further into Snowden and use the trees as cover to disrupt her speed advantage.
By the time Frisk had thought it through, he could already see the battleground and his opponent. The skeleton brothers were standing together off to the side. Looking over the human thought, Papyrus looked excited but nervous, while Sans… Sans held a cardboard sign that said 'Go Undyne!' scrawled almost illegibly in blue marker.
"Glad to know we have an unbiased audience." Frisk deadpanned and finally turned to inspect his opponent.
Undyne was still wearing her dark gray full-body plate armor, which made her look massive. Even though Frisk had shrunk, he was sure she had to be over six and a half feet tall in that thing. The warrior stood with her arms crossed, though Frisk could see her shaking slightly.
Maybe the cold was getting to her like he had hoped.
Taking a deep breath, Frisk marched up to stand before the giant.
"HUMAN," Her voice echoed from underneath the helmet. "As you have challenged me to a duel, I will wait for you to state your conditions for this match."
Frisk looked up at the armored figure and tried to appear confident. "If I win this duel, I request safe passage through Waterfall and that you no longer hunt me while I inhabit the Underground."
The human stared into the armored slits that held his opponent's eyes. He couldn't afford to show any weakness, even when negotiating the duel.
"Very well, and if I win this duel," Undyne reached out, and glowing blue energy that almost looked like water flowed out from her gauntlet to form her signature spear. "I will take your soul to give it to King Asgore and free the Monsters." She pointed her spear at Frisk's heart. "Do you accept these conditions?"
Some commotion came from the sidelines as Papyrus heard what was actually at stake. Luckily, Sans seemed to be able to calm his brother down, because the commotion eventually stopped.
Frisk's left eye lit up with JUSTICE magic as he gathered the energy into his hand. Lightning exploded from his fist with a clap of thunder and formed his bow. "I accept." He took a deep breath one more time.
"Great!" Undyne reached up and, for some reason, threw off her helmet. At that moment, she was no longer quivering in the cold; she was roaring to fight. "Then let us have a fair battle." She raised her empty hand in front of her face and did something weird with her fingers.
The human was getting ready to fight but when he was about to make his move, Undyne stopped and frowned at him. "Are you going to do the Seal of Confrontation too?" She asked, seemingly confused by his actions.
For a few seconds, Frisk stood there, struck by the absurdity of the situation. But maybe he should have expected this; Papyrus did say that he watched Naruto. Also, Undyne always seemed to take anime way too literally. She did think Humans fought with giant mechs, after all.
"This is how humans start a duel, right?" she asked, almost sounding embarrassed by his inaction.
Well, this might work better for his plan. "It's not exactly common practice when one of them is trying to kill the other." It's not common practice at all, but Frisk didn't feel like getting into that right now. He vaguely remembered Naruto and Sasuke doing this at the final valley, so maybe he could see where Undyne got this specific instance. "But it does seem rather fitting." So Frisk raised his hand and clumsily mirrored her hand sign.
"Haha!" The warrior shook off her embarrassment easily and lowered the sign. With impressive grace, she jumped back and started flourishing her spear. "HUMAN! For the sake of every monster in the Underground, for their hopes and dreams, I will defeat you right here and now!"
This was it. The time had come to implement his plan to beat Undyne.
Frisk pushed JUSTICE into his Aura before mirroring her same jump backward. However, this time, he backflipped for added effect. Landing with a pulse of yellow energy, Frisk twirled his bow around before pointing at Undyne with his free hand.
"Undyne! Even if I am weaker than you, I vow to win this duel here and now!" Frisk tried to sound as determined as possible. "Not only for my friends but also for every monster in the Underground. I won't allow you to stop me from saving them all!" He finished, his right eye glowing purple.
Yes, his master plan was to be a better anime protagonist than her.
"So come at me, and let me show the power I've gained from believing in myself and others!" He called out and watched as Undyne's face twisted in confusion.
Specifically, he constructed this whole situation to make her out as the villain of this story. It might have been manipulative, but Frisk knew that a lot of her self-worth came from viewing herself as the hero of the story. It was what allowed an ordinarily good person like her to justify killing a kid and stealing their soul.
"SO COOL!" Papyrus called out from the sidelines. He seemed to have overcome his surprise at the situation and had picked a side. Well, at least the audience was split evenly now.
Frisk hoped to use the fundamental incompatibility of her view of herself versus what she was doing to convince her to ally with him. From the humans, admittedly slim knowledge of psychology, he thought the cognitive dissonance would force Undyne to reevaluate her desire to kill him.
It definitely wasn't a foolproof strategy because when you challenge someone's beliefs like that, they can also respond with-
"Are You Mocking Me!?" Undyne screamed as her INTEGRITY magic almost exploded from her armor, covering it in a large dark blue aura.
Anger.
The shadows in the area seemed to lengthen, and Frisk's soul shone on his chest.
Yellow energy sparked, and Frisk dodged back toward Snowden before Undyne even finished her sentence. His preemptive leap was the only reason he wasn't flattened by the warrior's first blow, which cratered the ground where he had been standing.
Frisk wanted to keep running away but had already learned that wasn't very conducive to calming her down. So he reached further in his JUSTICE magic and aimed his bow. Two pseudo-arrows were shot in the span of a second, this time he hoped to capitalize on the arrows ability to destroy her water spears to land a meaningful blow against the armored opponent.
Undyne moved to block with her spear, but this time, the arrows were on target; the first would disperse her spear, and the second would hit her unarmored head. Frisk doubted it would do too much damage, but he had to show he was serious in this fight. The best way to do that was to at least trade some blows.
"Wha-" The human watched as Undyne aborted her attempt to block and almost instinctively threw herself to the side, easily dodging both attacks.
"Nice try Human! But your tricky attacks won't work on me." She bragged instead of capitalizing on his surprise. Reaching up, the Captain of the Royal Guard held her glowing blue spear in the air before slamming it into the ground. "You're fighting against the hero of the Underground!"
"You fight well, but I wouldn't call you a hero." Frisk shot back as he readied another arrow to fend off whatever attack his opponent was planning. "Wouldn't a hero try and break the perpetual cycle of violence between humans and monsters?" He packed more JUSTICE than ever into his readied arrow.
"Shut Up!" The water-like energy swirled and grew beneath Undyne before her JUSTICE mixed in. Lines of glowing yellow spears exploded from gathered power and hurtled towards the target of her anger.
Frisk released his charged arrow, and the two attacks collided in the air between them. The opposing electric and water-like magic crashed into each other and detonated. Both fighters stood their ground and watched each other through the explosions after effects.
Frisk was actually slightly surprised after realizing the blasts were equally matched. Undyne might have him in skill and speed, but their magical strength couldn't be that far off.
"You couldn't understand the pain of being trapped down here for our entire lives!" Another yellow spear formed out of the magic beneath her, but she didn't shoot it at him this time. "I fight so our King can free us from the prison you humans put us into." Frisk dismissed his JUSTICE and infused his Aura with PERSEVERANCE, hoping to take the enemy off guard with his durability.
They charged, and Undyne reached him quickly. Using something he learned from his lessons with Toriel, Frisk condensed a sphere of purple flames in his right hand. He hoped to tank the blow and deliver one in turn.
Unfortunately, once again, the warrior seemed to realize his intentions and used her yellow spear to deflect his right arm instead of just attacking him. Frisk, now overextended, took an INTEGRITY-enhanced armored elbow to the stomach, launching him back into one of the snowy tree trunks.
"Gah!" His fake Rasengan died in his hands as he felt the blow, even through his Aura. He immediately started to get up, his mind desperately trying to think of why all his plans were failing. It almost seemed like Undyne remembered their previous fight, but was that really possible?
No, it didn't matter right now. Frisk still had to continue with his plan, which might have given him another idea. "Is that really what everyone wants, to keep fighting each other until one of us dies?" He tried using the same line as before, while she might not remember it completely, maybe something would get through to her. "Is that really what you fight for?"
For a second, Frisk saw the determination in her eyes waver… DETERMINATION! Maybe that was why Undyne was able to predict his moves like she remembered their last fight. The Captain of the Royal Guard was always known to have the most DETERMINATION of the monsters in the Underground. It was just a theory, but it did make sense to him. He was getting through to her because she was having Deja Vu because of their argument in that discarded timeline.
Which meant he had to take advantage of it quickly.
"I know that I can only understand a fraction of that pain." Frisk had only been trapped here for… wow, how long has it been? It was difficult to keep track of all the resets. "But I'm still going to try and make it right! My goal is to free everyone, and I won't let you stop me!" His eye blazed with purple energy as he gathered PERSEVERANCE in his right hand.
This time, he charged forward with his spear forming mid-lunge. Unyne blocked it relatively easily, but Frisk did not overextend, so he wasn't blown away instantly. They entered a fierce close-range battle, where the human was forced on the defensive almost immediately. The difference in their speed and strength was too great. Not to mention that Undyne outclassed him in spear technique as well.
Frisk was basically self-taught in the art of the spear; his only formal training was sparring with Papyrus. While the skeleton wasn't a bad teacher, he couldn't hold a candle to Asgore, who had personally trained Undyne in spear combat.
So Frisk took hits, his Aura the only reason he could stay in the fight. Without JUSTICE enhancing his speed, it was all he could do to slowly allow his flame-enhanced Aura to drain away. Even trying to kick with gravity-enhanced power, courtesy of his ballet shoes, did nothing against the juggernaut.
"Let's see how your perseverance holds up to this!" Undyne swept her spear in an arc, and the human just barely managed to bring his spear to bear; the two opposing Magic Weapons hissed as fire and water fought against each other. The sheer force of the swing managed to lift Frisk slightly off the ground, and the more experienced spear user took advantage of his lack of leverage to score multiple quick thrusts.
The attacks left Frisk off balance, which was compounded when she slammed her armored foot into the ground and her form blurred blue, suddenly appearing to his left. It wasn't some sort of teleportation technique; she was just reducing the weight of her armor and moving fast. Multiple jabs of the spear later that he barely managed to defend and her form blurred once again.
This tactic worked even better for Undyne. Even with enhanced durability, his Aura was dropping quickly. He needed to do something fast.
Frisk ducked Undyne's next strike and rolled his spear to the crook of his elbow. With a clap, he brought his two hands together while channeling one of his opposing soul traits in each. Pushing that power into the ground, he watched his enemy's eyes widen, and she immediately jumped away.
The human did the same and watched as the earth erupted between them. That would only buy him seconds of time, and only because Undyne would be wary of any repeat attacks if she charged in. Frisk clenched his spear and thought hard. He needed some way to match her speed while maintaining the durability necessary to compete in close combat.
He couldn't use both soul traits to enhance his Aura simultaneously. He still didn't have the control to combine both elements without exploding, so without those, he was left with his shoes for magic.
Well maybe…
Watching as the dust settled from the detonation, Frisk studied Undyne across the small crater. Maybe her speed wasn't just from reducing the weight of her armor. That stomp she did when her form blurred was similar to what Papyrus did when he wanted to increase gravity with INTEGRITY magic.
Deciding to try it, Frisk raised his foot slightly and 'kicked' the ground with the ballet shoes. He had already known the enhancement only activated when he kicked something, but what exactly kicking was seemed to be broad, at least according to whatever logic the shoes ran on. Because Frisk was launched forward almost as quickly as he would be enhanced with JUSTICE magic.
He soared over the small crater and thrust his spear at the enemy. Undyne, caught off guard by his sudden leap, barely deflected the flaming spear. Though it did manage to singe her cheek with how close it got.
Landing awkwardly behind the stunned warrior, Frisk managed to not fall on his face, before he turned around. "I think my PERSEVERANCE will hold up just fine." He twirled his spear with renewed confidence. He might be exhausted, but he could tell she wasn't 100% either. "How will your INTEGRITY last while fighting someone with the same goal as you?"
Undyne flinched, and Frisk knew he had struck a nerve; the bubbling blue aura around her armor even dipped slightly. "I want to save everyone down here, the same as you." His right eye burned a stronger purple as if in confirmation. "I even understand wanting revenge, and if the humans who trapped your kind down here were standing behind me right now, I honestly don't know if I'd stop you."
Before he could continue, Undyne charged forward. "You're lying!"
She said that, but the aura around her armor had weakened. This didn't make it an easy fight, but it did make it more fair. Frisk was still slower in actual combat, though with her INTEGRITY weakening, Undyne's armor was starting to slow her down and reduce that gap.
"You don't actually believe that." Frisk's Aura flickered as he barely dodged another blow. Actually, using the shoes during combat was challenging to get the hang of. "You can see the truth in my magic just as I can see it in yours. You can't convince yourself that this is still the right thing to do."
"You're wrong!" Undyne threw her spear of yellow energy, and Frisk was forced to sacrifice his own weapon to stop the attack; even then, it still blasted him back. Slamming her hands into the ground, she created a giant whirlpool of blue energy at her feet from her own magic. Once again, spears started to explode from the swirling mass; more than thirty spears attacked him from all directions.
However, this time, they weren't enhanced by JUSTICE. So Frisk dug into the last stores of his JUSTICE magic to create an omnidirectional blast of electricity that disrupted each spear and made the attack useless. The human sighed in relief and almost fell to his knees from his overuse of magic.
Undyne looked at the triumphant human with conflicted eyes. "I-I have… Asgore's plan still needs your soul to break the barrier." The remnants of her whirlpool formed a single blue spear in her hand. "If you make it past me, the King will be forced to fight you." She dashed forward and thrust her spear.
Frisk panted as he stood back up and manifested more purple fire into his hands. He didn't have enough for a full spear. But his opponent's attack was slow compared to what she was capable of, so the human could grab the spear as it was thrust at him. The blue and purple energy clashed once more.
He was losing, and his Aura flickered like a light. But Undyne wasn't even using her own conviction anymore. She was just pushing herself forward for Asgore's plan, which meant his meta-knowledge was actually helpful for something.
"Asgore doesn't even want to go through with his plan!" Frisk's Aura shattered, but the flames of PERSEVERANCE didn't leave his hands. The blue spear dug into his skin, but he didn't falter. "H-he could have absorbed one of the souls and crossed the barrier to gather more any time he wanted."
The pressure behind the spear vanished as Undyne backed up as if physically struck. "Wha- That can't be right! His plan is the hope of the entire Underground!"
Frisk coughed and slowly brought his bleeding hands up. "Isn't it his job to give his people hope?" He asked but didn't wait for an answer. "Can you truly tell me that the Asgore you know would relish the chance to bring down vengeance upon anyone?"
Something flashed through her eyes, and Frisk knew she believed him. The King might act scary, but he was actually a big ball of fluff, kindness, and incredible guilt. "That's all we have, all I have, to believe in a better future," Undyne muttered, trying to come to terms with what she had heard. "Without that… what happens?"
"I don't know." Frisk brought his damaged hands forward to make half the Seal of Reconciliation… So what if he knew how to do it? He was a weeb, too. "But I know we can try to do whatever it is together."
The heavily battle-damaged forest was silent as everyone waited for her response. Even the skeleton brothers watched the scene without a peep.
Undyne's spear melted into the ground, and she slowly reached out to hook her fingers around Frisk's. "I-I guess I could use the help, trying to figure something out and all." The two fighters completed the Seal of Reconciliation. "You're not too weak, I guess, and it should be easier with more than one strong person working on it."
Relief flooded through Frisk as the last drops of PERSEVERANCE magic left his body.