“What’s this all about?” Undyne asked as everyone gathered together.

Alphys was there for Undyne’s sake and Sans was there because he was curious. Asgore was kind of uncomfortable with all this, and would rather be gardening. No one had objected to his absence. Frisk, of course, had to be present for this reveal.

“We’ve decided to bring you in on something that’s top secret, so you can help train Frisk better,” Alphys said.

“Sounds interesting,” Undyne said with a grin. “Secret technique or something?”

“Eh, more that I’m not as much of a badass as you think I am,” Frisk said with a smile.

“Ha! That I’d like to see. You’re something else, Frisk,” Undyne said.

“More than you think,” Frisk said dryly.

“So, it’s very, very top secret,” Alphys interjected. “This information is dangerous. You have to be careful.”

“Of course!” Undyne said with a grin.

“no one’s as careful as undyne,” Sans said. “except maybe papyrus.”

He got a few snickers and a halfhearted glare from Undyne for that.

“I have a secret power,” Frisk said. “Kind of like a superpower.”

“And you told me anime isn’t real,” Undyne said with another grin.

“Ha ha,” Frisk said dryly, but then laughed for real, shaking their head. “Anyway. I can lock time down in a spot, and then return to that point in time whenever I feel like it. Or whenever I die.”

“Wait,” Undyne said, frowning. “What does that… you can go back in time?”

“Only to the point I’d saved,” Frisk said. “Not a very flexible power.”

Sans and Frisk had figured it might be best not to tell anyone about the fact that they could technically go back to the day they fell into the underground. No sense giving anyone else any nightmares about everything being undone.

“Wait a second,” Undyne said. “Hey! Wait, this means you can’t be beat, doesn’t it?!?! You can just go back and try again!”

Frisk laughed.

“That’s absolutely correct,” Frisk said. “You actually killed me over a dozen times, the first time we met.”

“I did?” Undyne asked and then her face fell. “Oh. Uh. Sorry about that. At least we’re best buds now!”

Frisk shrugged.

“It worked out in the end,” they said. “But the thing is, I’d like to do something more intense than basic fitness and the gentle sparring training.”

“You want to fight me for real,” Undyne said and then grinned hugely.

“Well, uh, no,” Frisk said, and gave Sans an abruptly awkward look. “I, uh, don’t want to actually hurt you.”

“But if you did, you could just go back and undo it, right?” Undyne asked.

Frisk wrung their hands together.

“frisk needs training on how to control their intentions in their strikes,” Sans said.

“This sounds perfectly safe!” Undyne said. “Let’s do it!”

Alphys was giggling happily and Sans grinned. Frisk spluttered nervously.

“I really don’t want to hurt you,” they muttered.

“Then undo it!” Undyne said, getting up. “Come on, let’s go, the gym will be great, let's move!!”

“c’mon, kid, you know there’s no stopping this now,” Sans said and Frisk awkwardly got up.

They made their way to the gym, which wasn’t currently being used. Frisk sighed, looked over at Sans, and manifested a save point near the door.

“Hey, was that the thing, the locking down of time thing?” Undyne asked.

“Yeah,” Frisk said. “I call it saving.”

“You did that right before we fought,” Undyne said. “I remember thinking you were weird.”

Frisk and Alphys both snorted at that.

“you were right,” Sans said blithely, making Frisk outright cackle. He turned to Frisk. “you like to use a weapon, right?”

“I… er… yeah,” Frisk said. “Never fought bare handed.”

“i know just the thing,” he said. “be right back.”

He stepped out the door, and hardly two seconds later, came back with a stick.

“Where did you get that from?” Undyne asked.

“i took a shortcut,” Sans said and Frisk grinned hugely.

He tossed Frisk the stick.

“That’s hardly a weapon,” Undyne said.

“That’s the point,” Frisk said, looking at it fondly. “I don’t want to hurt you.”

“I don’t want to hurt you either, but isn’t the whole point of this to really try?” Undyne asked. “Because if accidents happen, it can just be undone?”

“I want you to try to kill me with everything you have,” Frisk said. “If you succeed, I’ll reload.”

“When we'd fought for real, I never even came close to beating you,” Undyne said. “You’re a natural.”

“No, I’m not,” Frisk said. “I just have more combat experience than most people ever will.”

“Well, good,” Undyne said. “Then try to kill me, too!”

Frisk flinched hard at that and shook their head.

“You’ve never even hit me, other than those little taps during a spar,” Undyne said. “Your power’s real, right? So gimme all you got!”

Frisk’s knuckles were white on their stick.

“M-maybe just starting with Frisk on the defensive?” Alphys suggested. “They seem nervous.”

“Sure,” Undyne said. “But you gotta show me what you’re made of eventually. You ready?”

“Absolutely,” Frisk said.

With no further warning, Undyne released a surge of magic, enveloping and trapping Frisk. With casual ease, Frisk directed the magic of the bubble into a shield of sorts, their chains also their protection. They’d done the same thing that first day.

Now pinned in place, Undyne let out a series of spear attacks, probing.

Frisk shook their head, effortlessly blocking them all.

“You honestly can’t kill me, even if you give me absolutely everything,” Frisk said. “Probing attacks aren’t going to accomplish anything. Pretend I’m about to kill Alphys or something.”

Undyne’s eyes narrowed and another series of spears flew out, swarming Frisk from all sides. Again, with seemingly effortless ease, they twisted the magic of their bindings to catch the attacks. They were grinning, though, and they were focusing hard.

“Good!” Frisk yelled, their eyes flashing with delight. “But you’re gonna have to try harder than that!”

Abruptly, their eyes widened and they choked. Their guard was down and their eyes were glazed, lost in another time and place. An expression of horror covered their face.

Another series of spears was mid-route and slammed through Frisk without even a token defense to block them. They did not react in the slightest. Frisk fell to their knees, not seeming to notice the attack, but tears started to flow as they began to shake, covering their face.

“Uh, Frisk…?” Undyne asked, sharing a perplexed look with Alphys.

If you stumble upon this narrative on Amazon, it's taken without the author's consent. Report it.

Sans sauntered over.

“you okay, kid?” he asked.

“I… I said… it was exactly what Undyne said, when…” Frisk choked out. “I can’t believe I…”

“it’s alright,” Sans said. “undyne’s confused, not upset. no one’s hurt. think you maybe need to heal more? you can’t do this training yet?”

Frisk shook their head aggressively.

“I’m scared I’m going to hurt someone,” they said. “You were right, Sans, learning this will help. I just need to… I need to get my head in the game.”

“anything i can do to help?” Sans asked.

Frisk abruptly looked away.

“c’mon, tell me what it is,” Sans pressed.

“I’ll do anything for you,” Frisk said, not looking at him. “Without second guessing myself. Without overthinking it. I’ll just… obey you.”

“so, what, if i just tell you to do it, that’s all it’d take?” Sans asked.

Frisk nodded, still not looking at him.

“uh, ok,” Sans said.

He paused, looking thoughtful for a second.

“frisk,” he said. “here’s what you’re gonna do. you’re going to attack undyne for real, giving it everything you’ve got. you’re going to try to keep an eye on her health, but you’re going to trust her to tell you when it’s too much. you’ll back off the instant she does.”

Frisk stood, their expression transforming in a way that creeped Sans out hugely. Their gaze was resolute and determined, looking at Undyne with a cool expression of deadly intent. Undyne instantly got more guarded on seeing it.

“you heard all that, undyne?” Sans asked.

She nodded.

“I’ll warn them, don’t worry!” Undyne said.

“remember that it’ll hurt them badly if they accidentally kill you,” he said. “play it extra safe for a while, okay?”

Undyne held her spear ready and nodded.

“you both ready?” Sans asked.

Frisk and Undyne nodded.

“start,” he said, and Frisk raced into motion.

With an arc as perfect as it was chilling, Frisk’s stick moved to hit Undyne. She tried to block, but Frisk’s focus was absolute. Sans could see the ripple run through Undyne as the hit was absorbed. Blocking did nothing against a human's killing intent.

The battle unfolded into a thing of beauty that only Sans could fully appreciate. Frisk moved with practically precognitive ability, knowing Undyne’s attacks intimately. The same thing started happening that Sans had noticed in their first battle, in this timeline - Frisk was dodging and moving much more intently than strictly necessary, as though dodging attacks of greater intensity than they were actually facing.

Again and again, Frisk launched deadly strikes of true killing intent against Undyne, and Sans could see her body start to strain under the assaults.

It wasn’t that Sans had any doubts remaining prior to this fight, about Frisk, their history, and all that. But once again, those already non-existent doubts were ground into the faintest dust. He’d been convinced, but that conviction deepened as he watched Frisk’s deadly dance.

He watched the nightmare that the genocide Sans had witnessed, the Angel of Death that had killed literally everyone. Even the cool conviction as they moved - when they were committed to a course, this is what they were like. Even if they didn’t really want to be. This was the thing that had killed Papyrus.

Well, partially.

He had been well trained with evaluating things like EXP and LOVE, once upon a time. It was strange, seeing Frisk move with such clearly practiced killing intent, yet it lacked the true intensity, the true edge that came with LOVE. He’d believed it was a quality of the soul, a purely mental / emotional / spiritual thing, but it was something that didn’t come with the resets.

It was something… maybe not “physical,” exactly, but something that wasn’t just the mind. He’d never seen anyone who’d acquired it - nearly max amount, as far as he could tell - who then managed to get rid of it. Reduce it, sure; that just took time. But removing it?

He kinda wished he could get rid of his own. But so far as he knew, no one in this world had learned how to evaluate it, so at least his secrets were still safe. Also he felt kinda cheated - he still had the numbing, distancing effect of his own gained LOVE, but with his unstable core, he couldn’t attack or defend properly. All that LOVE, earned the hard way, and not an ounce of benefit from it anymore.

It didn’t take long before Undyne called the fight, cheering as she did so, and praising Frisk’s skill.

“That was amazing, Frisk!” Undyne said. “Where’d you learn to fight like that?”

Frisk looked away sharply, awkwardly.

“Don’t worry about it,” Undyne said, showing that she could actually notice boundaries, though maybe only when the person had collapsed into a crying mess just before. “But I’ll need to heal up. And I know exactly what you need to work on!”

Frisk silently pulled out a piece of pie and handed it to Undyne, who ate it happily and moaned a trifle awkwardly at both the taste and the infusion of healing magic.

“You move like you were born on a battlefield,” Undyne praised, and Frisk flinched again. “But your attacks are a little too serious. You need to try to move the same way you have been, striking the same way, but try to see if you can knock me away, instead of kill me. Same hits, same movements, but focus on moving me. You got it?”

“I do,” Frisk said. “You ready?”

“Let’s do this!” Undyne yelled.

Frisk glanced at Sans uncertainly, and he nodded. As soon as he did so, their gaze sharpened once more, all doubts vanishing from their face.

Yeah, that was creepy.

The next battle progressed, and Frisk was honestly kind of terrible. They kept looking vaguely confused as they attacked, and their intentions were all over the place. Sometimes, they’d try to change the attacks physically, screwing up their otherwise perfect form. Sometimes, they’d accidentally strike with true killing intent. Sometimes, though, they’d land it, and Undyne would slide back from the impact.

Their defensive movements were still fantastic, though.

Two bouts later, where Undyne had to stop and heal, Frisk was finally getting worn down enough that Sans called it for their sake.

“you’re looking pretty grey, frisk,” he said. “you need to watch your limits, too.”

“I am,” Frisk said. “I can probably take two or three hits without dying, I’m fine.”

“that’s… pretty close to being dead,” Sans said.

“Not really,” Frisk said. “I’ve pushed it way harder than that before.”

“how hard were you thinking of pushing it?” Sans asked.

“Where I am certain I can take a single hit without dying,” Frisk said. “That’s my usual point to call it.”

“where two hits would kill you?” Sans asked, and they nodded. “that’s cutting it a bit close.”

Frisk shrugged.

“When you have limited healing items, it’s important to ration them carefully,” they said.

“i’d like the timeline not to be reset, if possible,” Sans said dryly. “let’s call the limit at the point where you can safely take three hits.”

They frowned.

“That seems horribly wasteful,” they said. “Can we compromise on two?”

“fine,” Sans said. “but if you ever mess up and reset, then we’re moving to the three hit limit.”

“That’s motivation to make sure I don’t screw up,” they said with a smile. “One more hit, then.”

The battle resumed. Undyne was vastly more physically fit than Frisk, and that difference started to become apparent. Frisk was slowing down, and it wasn’t long till they took that last hit. They healed, and tried again, but it was a losing battle. Their dodges and strikes quickly became slow and inadequate.

But they kept trying. Undyne was finally more in her element, facing an enemy at a more reasonable level of skill. Frisk threw themself at the battle without any care for their body’s limits. They were leaving a small puddle of sweat anywhere they stood, and they were breathing in great bellows.

Sans was kind of morbidly curious how far Frisk and Undyne would push it before someone gave up. Considering the two people involved, he honestly had no idea, other than that it would be far past the limits of sanity.

He fell to his curiosity and just watched.

Undyne’s strikes were well done, intent wise. They were tempered enough that Frisk was easily taking a solid ten strikes safely, but still sharp enough to make Frisk need to honestly try to dodge. Which they did, again and again and again.

Until finally, their legs just refused. He saw the muscles clench, but instead of a leap to the side, their leg shook and collapsed, leaving Frisk fallen to the ground in a puddle of sweat. They started throwing up, though it was mostly water. Apparently they hadn’t been eating a lot of human food lately.

Undyne grinned at them and stood with her spear’s butt planted into the ground, not even looking winded.

“Had enough?” Undyne asked brightly.

“I… can still… fight…” Frisk managed, dragging themself back to their feet.

“Is that so?” Undyne asked, and leaned forward, poking them in the head.

Frisk fell back to the ground, their legs twitching as they tried to stand again.

“I love the willpower!” Undyne yelled. “But you need to do a critical step in your training process!”

“What’s that…?” Frisk said, managing to stand on wobbling legs again.

Undyne grabbed them and hoisted them over her head.

“Resting!” Undyne yelled. “Alphys! Let’s go to your place with some snacks and anime!”

Sans was chuckling to himself. Looked like Undyne had this well taken care of. Frisk should be safe training.

Though if they were going to spar like that again, he’d want to come watch.

Time passed, and things had changed with Frisk’s training. Undyne was pushing their body hard, for strength and endurance both. When sparring days came, sometimes Undyne would have Frisk wear a weighted harness. She’d insisted it look like a turtle shell for some reason, but it slowed Frisk down enough to actually let them work on improving their combat skills.

That said, they already had about as much real combat experience as most ten year veterans. Usually, combat only lasted a few minutes at a stretch, but reloading restored Frisk’s stamina. They’d experienced hours-long battles at high intensity, at full strength. Plus, being pushed to their true limits in ways no living person could ever have experienced.

It didn’t take long before Frisk started to really get the hang of modifying their attacks’ intentions, and they grew far more comfortable. Having these battles end safely - and they never made a lethal mistake, never reloading, though it got close a few times - was clearly good for their mental health. And physical training was good for them on multiple levels, too.

Sans’ original idea was to have them break away negative associations of battle with some relatively gentle sparring, along with training on controlling their intent.

But now he was thinking they should just keep it up. Undyne loved having such a dedicated student, and Frisk was enjoying themself, too.

It wasn’t like he actually had a say in it, but if the topic came up, he’d weigh in. It was good for them.