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Published:
2024-12-23
Updated:
2026-01-30
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13/?
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A Disastrous Experiment

Summary:

Saiki wakes up with a problem he's never dealt with before. Morning wood. His decision on what to do about it leads to several mortifying interactions he would much rather pretend never happened, and the fallout uncovers burdens he's tried to keep hidden from everyone - including himself.

Like I mentioned in the tags I'm not completely sure how graphic something needs to be to earn the "graphic depictions of violence" warning (I'm very new to AO3) but towards the end of the story I did write a couple somewhat violent scenes. While I don't think I wrote anything that you couldn't find in a shonen anime, I did show a bit more mature content than the Saiki K. anime ever does and at times I used much more candid language to discuss things. See the notes before each chapter for more specific warnings wherever they apply.

Notes:

Chapter 10 updated September 21st 2025

A Disastrous Experiment is still on indefinite hiatus.

Chapter 1: The Ill Advised Experiment

Notes:

Warnings:
This chapter includes some mild sexual content. I really mean mild though, if you can't figure out where it's going from the summary it may very well fly right over your head. I don't describe anything. I also don't really use any euphemisms though, so I guess if you're averse to reading words related to sexual activities then steer clear.

Other important stuff:
This story takes place a couple months into Saiki's third year of high school, after both the volcano and meteor incidents. For the sake of plot convenience/continuity (and also because I think it makes the most sense) I’m considering the timeline to work as follows: Toritsuka shows up in the first iteration of Saiki’s second year of high school. Saiki fails to stop the eruption, resets the earth back a year. Same happens in the second iteration where Kuboyasu shows up, the third where Saiko arrives, the fourth with Aiura (this is also the year he started manifesting his abilities over time), and the fifth with Akechi (also when he started experimenting with deliberately using his time manipulation abilities). Suzumiya shows up in the sixth iteration, and this is also when Kusuke gave Saiki the limiter that would completely erase his powers. At the end of this school year, he attempts to halt the eruption with the help of Aiura, Toritsuka, and his clones. They fail on their first try, but because they were really close and Saiki’s time manipulation abilities have grown, he instigates a one-day time loop instead of resetting the earth by a year. They get closer on their second try, and finally succeed on their third attempt. However, his friends find him, so he has to repeat the process one more time, now having disabled the helicopter. So in total, Saiki reset time for the earth by one year five times, and attempted to stop the eruption eight times before finally letting time move forward again after everything went smoothly on his ninth attempt. (Hopefully I got all that right, it was hard to keep track of.)

Optional rambling:
I tried my best to keep everyone in-character but this is the first time I've written characters like this. I think I did a pretty good job with their personalities given the dumb story premise, but it took me a bit to get into everyone's voices, particularly Aiura's. Apologies if they seem a little off.

A note on Saiki's gloves: For the sake of plot convenience (and also to save words) I've made it so that his gloves only block involuntary psychometry, but Saiki can still use it deliberately through his gloves with a bit of effort. I feel like this is a reasonable extrapolation from canon and it makes things a lot more convenient to write.

A note on characters: Toritsuka shows up in chapter two and plays a moderately significant role throughout the story, and I think I made him a slightly better person than he is in canon, or at least a bit more self-aware and an actually really good friend. Everyone else should be pretty in-character. I made up a bit of backstory for Aiura since she doesn't really have any in the anime, nor any family, so I gave her an aunt.

Anyway, I'll stop rambling. Enjoy!

(See the end of the chapter for more notes.)

Chapter Text

Saiki sat at his desk, staring down at the stubborn bulge in his pants and trying to decide what to do. It had been there when he woke up — the product of some dream that he, strangely enough, couldn’t remember. He’d tried to ignore it as he got dressed and finished his weekend homework. He’d assumed it would go away. Apparently not. Perhaps he just had to give it more time.

This was the first time he could recall ever being sexually aroused, and he was unsure how best to respond.

Saiki moved one hand off the armrest of his chair and started to reach for his pants. I guess I am curious…

He shook his head and put his hand back firmly on the armrest. No, I don’t want to be like Toritsuka. Then again, this is a normal high school boy experience, and I do want a normal life. Most guys have done this plenty of times by their senior year. Besides, I don’t know the next time I’ll have this opportunity. It would be a shame to waste it, maybe I should try after all. If nothing else, it could be informative.

He was still debating with himself when his hand reached the button of his pants. It seemed he would do this. Mouth dry and heart racing, he undid his pants and reached inside. Last chance to back out…

Saiki didn’t.

“Ku, why haven’t you come down yet?” His mom’s thought from just outside his room.

“Honestly,” Saiki’s dad this time, “Kusuo what’s taking-”

Saiki teleported away to a tiny deserted island just as the doorknob turned. That was one normal experience he did not want.

It’s probably for the best anyway, he thought. Sneezing causes random things around me to explode, I don’t know what orgasm would do. This is definitely safest if I’m going to continue with this experiment.

He let out a short sigh of relief, realizing only then that he was levitating about five meters up in the air and still posed as if he were sitting in his desk chair. Shaking his head at his own foolishness, Saiki lowered till his feet touched the ground and leaned his back against a palm tree, his hand resuming its motion. He had to admit, the sensation was pleasant, if a little odd. As he kept it up, his mind wandered to thoughts of Aiura. Thoughts of her voice; “I’m yours.”

Good grief, I will not be a creep like Toritsuka! Think of something else. Saiki tried, but his thoughts kept returning to the irritating psychic, his hormone addled brain constructing more and more lewd scenarios. This is normal too, isn’t it? And it’s not like she would mind, she’d probably be overjoyed I’m thinking about her at a time like this.

It made him feel like a creep though. His mind and body seemed to disagree with each other; while his body was quite happy to keep it up, he was starting to wonder whether this had really been worth all the effort. He just wanted to hurry and get it over with so he could go back home and eat breakfast.

Saiki turned so he was facing the tree and braced his free arm against it, pressing his forehead to his wrist and squeezing his eyes shut. That just let his imagination become even more vivid. Saiki gave in and entertained the fantasy, figuring it would help hurry things along. He was right. Saiki gritted his teeth.

“Come on, do you really have to be thinking about her as you, oh, ahh!”

His body jerked.

Crackling sounded all around him as Saiki sank to the ground, trembling and panting for breath. His limbs felt like jelly. Even the thought of his favorite dessert only triggered a spark of interest for him in that moment. He took a second to bask in the aftereffects of his experiment.

Basking done. Opening his eyes, Saiki straightened his clothes, then stood and surveyed the island. The top half of the tree he’d been leaning against was gone, and the few other trees around were all engulfed in flames. Several piles of dust sat in the place of what had been large rocks. The island was also split down the middle.

It had survived remarkably well. Still, he felt bad, so he used his restoration to rewind the island back to the condition it had been in yesterday. The nice aspect of being out here in the middle of nowhere was that he didn’t have to clean up any mess in his room, but he wouldn’t just leave the island completely destroyed.

Saiki decided his experiment had indeed been quite informative. But while it had been pleasant enough, he wasn’t sure he’d ever bother with a repeat. Maybe if another opportunity arose. However, he certainly wouldn’t be seeking it out. The whole thing seemed like a good deal of effort for something so short lived. Coffee jelly was much better.

He hadn’t quite caught his breath by the time he was finished cleaning up after himself, but he figured it was time to head home. If his parents did notice that he was a bit out of breath, they’d probably attribute it to his fleeing a cockroach or something. It wouldn’t be the first time he teleported away due to a bug.

Letting out a brief sigh, he sat down in his chair, once again back in his room. Except, he wasn’t in his room.

“Eh. Aiura.”

“Saiki! What’re you…” Aiura’s gaze drifted downward to his lap, and her eyes widened. “Eeek!”

Blinking once, Saiki pulled his own attention away from the half-dressed Aiura, instead staring at the pink polka dotted — odd but very Aiura like choice — wall and spinning the chair away so his back was to her. He had to quell the urge to correct her on his name. She’d been calling him ‘Kusuo’ less and less over the past couple months, and it was still jarring every time she called him by his family name. If he wanted to know why she’d made the switch it wouldn’t be hard to find out, but for some reason that he didn’t want to examine, Saiki shied away from learning the answer.

So instead of asking why or reading Aiura’s mind or correcting her, he said, “Hurry and finish changing.”

“Oh?” Aiura said, moving closer to him. “Does the sight of my body stir some interest in you at last? You did just like, appear in my bedroom while I was in the middle of changing.”

“Why do I get the feeling you were changing because you knew I was about to pop in?”

“Eh, well…” Aiura said, stepping back again. “I didn’t exactly know that, I was just looking at our compatibility — it went up by the way — and I got a premonition that if I stood in that spot and changed into this other outfit, our compatibility score would increase again.”

“And what’s it at now?” Saiki asked, trying not to be so aware of the rustling sounds of Aiura dressing. He had no interest in naked bodies. There was nothing special about Aiura’s, it shouldn’t affect him any more than anyone else’s.

“Hm? Oh, uh, let me check. Oh!” Aiura added the thought, “You can turn around now by the way.”

“What was that ‘oh’ about, what’s it at now?”

“Seventy eight percent compatible.”

That doesn’t sound so bad, Saiki thought to himself, turning back to face Aiura. “It’s not even that close to eighty five percent, didn’t I hear you telling someone a week back not to settle for a marriage with any less than an eighty five percent compatibility score?”

Aiura nodded and moved to sit on her bed. Her king-sized bed. Why on earth did she have such a large bed? And why did Saiki notice how good she looked in her pale pink and rose sweater and navy mini skirt? Those two thoughts had nothing to do with each other, he was positive. Why did she have hot pink leopard print bedding? There, that was a much better thing for him to question. It matches her curtains.

“I mean, yeah, I did, but compatibility can change,” Aiura said with a shrug, leaning back on her hands. “And besides, we’re soulmates. I know it’s just a matter of time before we’re totes at a hundred percent! I mean like, it’s already gone up quite a bit.”

“What was it at when we first met?”

Aiura sighed. “Only like, fifty nine percent, it’s one of the reasons it took me so long to figure out that you were my soulmate. I checked my compatibility with everyone when I first realized I couldn’t see auras at school. My highest compatibility was sixty eight percent with Kuboyasu, and I knew he wasn’t who I was looking for.”

“If you had a higher compatibility with him why didn’t you just ditch me and try to go for Kuboyasu? I’m sure he would’ve been happy to marry you.”

“His compatibility wasn’t high enough for me to bother, not when I knew you were lurking around somewhere.”

“You don’t have to say it like that.”

“Well, anyway,” Aiura said with a vague wave. “Our compatibility has been gradually increasing over the course of our friendship.”

“I suppose I do tolerate you more than I used to, and you have helped me out of a few jams.”

“I have, haven’t I?” Aiura smiled and crossed her legs. “Still, it was like, creeping up really slowly. I checked when I woke up this morning like always and it was still only at sixty five percent.”

“It only went up six points? Where did the rest come from?”

Aiura nodded. “Three of those came during the volcano incident.” Oh I love you so much!

Saiki ignored that thought. It wasn’t really directed at him anyway, just triggered by the memory of him stopping the eruption.

“Huh, our compatibility just went up another point.” Aiura stared at him, but Saiki was sure his face stayed blank. “Our compatibility jumped up from sixty five to seventy four just a minute or two before you popped in here. Nothing about me has changed, so it must’ve been something you did.”

Saiki knew his blank expression faltered, and his grip tightened on the armrests of Aiura’s chair until one cracked beneath his fingers.

“Your breathing has been kinda ragged since you arrived, and you got flustered instead of exasperated when you saw me in my underwear. Add to that the way your body responded…” Aiura gasped and clapped one hand over her mouth, eyes wide. “Saiki, did you-”

“Don’t finish that thought,” Saiki ordered, shooting to his feet.

“And to thoughts of me!”

“How did you know?”

Aiura’s cheeks reddened. “O.m.g. I was right? You really did!”

“You’re evil. It was an experiment, nothing more. I knew it was a bad idea.”

“But you still, like, did it,” Aiura said, lowering her hand and giving him an evil smirk. Then she snickered. “You jacked off to dirty thoughts of me and then teleported into my room while I was changing.”

“Don’t say it like that! You’re making me sound like a creep!”

“You just couldn’t get enough of me in your mind, so you came here for the real thing,” Aiura said, looking down and tilting her head to the side. “All you have to do is ask, I’m yours for the taking. Don’t worry about being gentle with me…”

“Stop trying to seduce me, it won’t work.”

“Are you sure, Kusuo?” Aiura asked, her voice soft and sweet. “You know, I act all forward, but like, it’s kind of a lie, I’m actually really inexperienced. I mean yeah I’ve made out with a few guys before, but this’ll be my first time. So like, while I don’t mind if you want to be a little rough, please try to temper your strength…”

Saiki blinked, trying to come up with a response, but it was hard with Aiura sitting there on the bed, projecting all her thoughts to him.

“I want you- Aha!” Aiura suddenly shot to her feet, pointing to his groin with a triumphant grin. “I knew it, you are into me!”

“My eyes are up here,” Saiki said, spinning to face the wall and moving to stand in the corner. “And my body’s betraying me, ignore it.”

“Oh? Are you sure it’s really betraying you, and not just looking out for your best interests?” Aiura sounded as self-satisfied as Amp after tricking another human into becoming his servant.

“I’m positive, now stop staring. You’re making it worse.”

“How do you know I’m looking at you?”

“I can feel your regard. Besides, your thoughts are rather obvious.”

“Hmph, alright, you caught me,” Aiura said, raising her hands and turning her gaze away from him. She also cut down on the lewd thoughts.

“You wouldn’t want to seduce me anyway, not unless you want your house trashed and your room destroyed.”

“Oh!”

“Not like that, stop with those thoughts!”

“Sorry, I can’t help it when you say something like that.”

Saiki gritted his teeth and moved to look out the window. It put him a little closer to Aiura, but he needed fresh air. He leaned on the sill with both hands, using psychokinesis to open the window and letting out a relieved breath as Aiura got her thoughts mostly under control.

“So like, what did you mean? Destroying my room sounds pretty intense.”

Saiki sighed, studying the skyline and the people below. “It seems that when I orgasm, I explode objects, set my surroundings on fire, disintegrate large portions of rock, and might cause very localized earthquakes.”

“Wow, that’s intense,” Aiura said. “Wait, does that mean you destroyed your house? Is your family okay? I hope they were out while you…”

She trailed off, noticing Saiki shaking his head.

“I teleported to a deserted island for this experiment,” Saiki said. “That’s why I had to teleport back. I must’ve come here by mistake because you were on my mind- don’t get so smug! Anyway, I’m recovered now and it’s been more than three minutes, I’m going home.”

He teleported back to his room. Except, nothing happened.

Why isn’t it working? Saiki stared down at his hands, still gripping Aiura’s windowsill.

“Like, are you sure you’ve, ah, caught your breath?” Aiura asked, her voice full of only partially suppressed laughter.

“I’m sure, I just need a moment.” Saiki tried again, and again nothing happened.

“Hmph! Was it too intense for you?” Aiura asked, giving up on holding back her laughter. “I bet you only lasted, like, three minutes too!”

“Do you really think it’s wise to tease me about this?” Saiki asked, turning to look at her with his menacing face.

She wrapped her arms around herself and laughed harder, but it soon died away and her expression softened into a gentle smile. Saiki was again bombarded by her thoughts, but this time they were only warm feelings of immense love.

“I know you’re a good person, Saiki Kusuo,” Aiura said, standing and crossing the short distance between them, stopping less than half a meter away with her hands clasped behind her back. “You wouldn’t ever abuse your powers. Like, even now, you’d rather be embarrassed than use your powers unnecessarily to wipe my memory of this incident. And it’s not just because it’s me, I know you’d do the same if it was anyone else who knew about your powers.”

“I wouldn’t be embarrassed if I was talking about this with anyone else, I don’t care about their opinions.” Saiki’s eyes widened and he quickly turned back to look out the window. Crap, did I really send her all that? What a pain, she’ll take that as a confession that she means more to me than anyone else.

Which was ridiculous of course, he was barely fond of her as a friend, she was certainly nothing more to him. Even if she was the only person he’d ever gotten aroused over. Saiki jolted as something soft and warm covered his hand. He stared down at Aiura’s delicate fingers now resting atop his, then looked up to her smiling face.

“Your eyes are so pretty, I wish you’d like, wear transparent glasses or something so I could see them clearly more often.”

Saiki stared at her in surprise.

She said nothing more, but her thoughts were enough. It was hard to stay embarrassed in the midst of all that love.

Shaking his head, Saiki tried to teleport once more. Nothing. He sighed.

“You know,” Aiura said a few moments later, “I think I might have an idea why you can’t teleport.”

“What’s that?”

Aiura’s smile turned smug. “I think it’s the same reason you came here by mistake, you like, subconsciously want to be near me.”

“That’s ridiculous.” Saiki shook his head. “I’m sure it’s something else. Maybe I’m allergic to something from that island and it’s making my powers act up.”

Aiura nodded. “I guess we should like, check your other powers to make sure.”

“Good, I’m glad you can be sensible,” Saiki said with his own nod. He hopped, picking his feet up and floating in the air for a few seconds. “Levitation is fine.”

So was pyrokenesis, clairvoyance, thoughtography, astral projection, invisibility, and psychometry.

“Here,” Aiura said, tearing a crumpled piece of scribbled-on notebook paper and handing it to him.

“I already knew my restoration ability is functional,” Saiki said even as he restored the paper. “I used it to fix the island before teleporting.”

“Hmm, how about this,” Aiura said, taking two crystal balls out of a drawer in her nightstand and handing the thoroughly decorated one to him. “This one was more expensive but the decorations on that one should totes make them equal value.”

“Apport. Still functioning,” Saiki said, handing over the undecorated crystal ball. “Everything seems to be fine except teleportation and-”

Aiura cocked her head and raised her eyebrows when he cut himself off.

“Teleportation and… what?”

Saiki shook his head and stared fixedly at the wall beside Aiura.

“Come on, Saiki,” she said, moving sideways into his line of sight. “You can tell me.”

Keeping the instinctive ‘Kusuo’ mental correction to himself, Saiki returned to the window and stared at the cloud speckled sky. “My x-ray vision is acting up as well. Usually when I activate it — deliberately or not — I can see down to muscle and organs, or even all the way down to the skeleton sometimes.”

“Usually,” Aiura said, following him to the window again and leaning over to look at his face. “But right now…?”

Saiki looked at her from the corners of his eyes. “Right now I can only see through your clothes.”

Aiura gasped in mock horror and stepped back, covering herself with her arms as though she were actually naked. “Saiki, I didn’t know you were the kind of guy to peep on an innocent girl! Do you at least, like what you see?”

“Relax, I’m not doing it right now. I turned it off as soon as I realized what was going on. Good grief.”

“Oh.”

“Don’t sound so disappointed! At any rate, I think it’s reasonable to say that most of my powers are fine. It’s really just teleportation that’s an inconvenience right now, but I’m sure it’ll return to normal any minute.”

“Wait, there’s one more I want to check,” Aiura said, closing the distance between them again. She rested one hand on his and used her other to turn his face towards her.

Saiki picked up on her thought a hair too late to stop her.

“Don’t, Aiura!” he said as she pulled his glasses off. Saiki squeezed his eyes shut, but he knew it was too late; he’d already seen her without the barrier of his glasses. He cracked one eye just a sliver, then opened both wide and stared at Aiura. She stood un-petrified, smiling at him and dangling his glasses from one finger.

“That was stupid, did you want to lose a day? Petrifaction is no joke, it’s not something to be careless with, it’s dangerous!”

“Aww, I didn’t mean to like, make you worry about me, I’m sorry.”

“No you’re not, yes you did, and I wasn’t worried about you.”

“Right, well, you should know I’m not that stupid,” Aiura said, then struck one of her goofy fortune-teller poses. “I looked into the future to make sure I was right before taking your glasses.”

“Mikoto, is everything alright in there? You’re missing breakfa-“

A woman opened the door to Aiura’s room and Saiki glanced over before catching himself. He snapped his eyes shut and jerked his head away, but the woman — Aiura’s aunt — was already stone.

“You should really give me back my glasses, my powers have returned to normal.”

“Mmm, nope!” Aiura said. “No petrifaction in my future, and I think it’s because-”

“Don’t finish that thought, you’re wrong,” Saiki said, glaring at Aiura. “I’m just a little rattled is all. Remind me to come back in twenty four hours for any memory alteration I need to do. I’m going home.”

“Wait, you can’t just leave!” Aiura said, grabbing his shoulder.

But Saiki was already teleporting.

He landed in the middle of his living room and let out a short sigh of relief. Home at last. Maybe he could forget about his little experiment and get back to his normal routine now. Except, he could still feel Aiura’s hand on his shoulder, and not only were his parents sitting on the couch staring at them, his brother sat in one of three chairs opposite the couch.

And Saiki hadn’t put his glasses back on.

“Oh my,” Kusuke said.

Notes:

Well that was fun. I hope you enjoyed! This is not only the first fic I'm posting here but also the first fanfiction that I would call a complete story I've ever written. In the past I've done little scenes and one-shots for different fandoms on the Amino app, but never anything longer than a few thousand words, and never anything with a whole plot. This thing is already almost 40k words and for some reason it's still not done so I decided to just start posting it. I plan on uploading a chapter every Monday Wednesday and Friday. I've currently got the first seven and a half chapters written (though I realized I messed up some continuity so they all need some extra editing) and most of several end chapters as well as the epilogue. (Yeah, I don't write in chronological order. Like, at all. It's kind of a problem.)

Anyway, see you on Wednesday!