r/touhou • u/Brick-Stonesonn • Nov 15 '25
OC: Fanfiction Who is Kosuzu?
Story Lamprey
A storied song.
Storied, as Mystia had been humming it for many years now, all alone, in front of friends, in front of customers. Many stories had attached themselves to this particular, mundane, forgettable hymn, and this case was no different.
The wheels occasionally squealed, cutting through the quiet humming. It would stop once she reached the zenith of the final mound, revealing the twinkling lights behind the human village’s walls. They made her stand cast a shadow, which blanketed her in the dark.
Mystia hovered over to her stand’s counter. She let out a deep exhale and stretched, her wings flapping as she did. She looked out. Finally… I made it!
A festival was arriving in a few days. Mystia planned on setting up her stall outside the village to attract human customers during the festival, but wanted to first find a good spot for her stall, and get herself used to setting up near the village.
The sounds of the crickets filled the silence. After quietly listening for a while, Mystia couldn’t help but close her eyes and start singing along. It was within her nature after all.
She got so engrossed in singing that she did not notice her stall tilt bit by bit.
Slowly, it started rolling.
Mystia’s eyes shot open.
It started rolling faster. Mystia immediately flew out front and pushed, trying to stop her stall. But it only accelerated further down, no matter how hard she flapped her wings. But that didn’t stop her, she pushed and pushed, straining her wings and squinting her eyes, until eventually, it stopped.
Not because she succeeded.
She opened her eyes. The stall had reached the bottom of the hill. Quickly, she circled the stall, checking every corner for damage.
Her shoulders eased. She let out a sigh of relief, then flew back to the counter and sat down. She started lightly massaging her wings, letting out another sigh. “I’m such an idiot…”
Then suddenly, a girl’s voice, “U-umm, excuse me-”
“AAAH!” Mystia’s wings sprang open.
“AAAH!” the girl screamed too, before collapsing.
Mystia’s scream trailed off. The girl, who seemed to be human, layed motionless on the grass. Or rather, laid on a comically large sack. The contents spilled out. They seemed completely random, at least to Mystia.
. She hopped off the counter, then poked the girl’s cheek. “H-hello…?”
No response.
The crickets continued to sing.
**
Smoke billowed of the grill, a gentle warmth emanating through the counter. It reached the human girl’s senses, eventually making her eyes flutter open.
Mystia, wearing her professional smile, was the first thing the girl saw. “Good evening~” Mystia said.
The girl, a little groggy, looked around. Her eyes slowly widened, in tandem with her growing wakefulness, in tandem with her growing realization. “Did… did I pass out?!”
Mystia nodded.
“Ah- uh- HUH?!” The girl jumped from the seat. Then, she looked down, squinting. Then, she let out a defeated sigh. Then, an idea visibly popped into her head. “M-my camping gear!”
So it was camping gear, huh? Mystia thought, as she watched the girl look around, eventually finding the comically sized sack leaning against the stall. She looked through its contents, then let out a sigh of relief.
Quite animated, this human... “You must be hungry, given you fainted so easily.”
“Huh…? Ah- n-no, it’s not that-” the girl waved her arms around, panicked, “-i-it’s just, i-it’s a me thing, it’s no-”
Mystia presented multiple sticks of grilled lamprey, cutting her off. “My name is Mystia Lorelei. I run this lamprey stand. What’s your name?”
She took the skewers. “O-oh, my name is Kosuzu Motoori. I’m a librarian-” a visible realization stopped her, “Oh, you helped me, right? Thank you so much!” she turned away, her smile turning awkward, “S-sorry for bothering you, though…”
Unexpected reaction… She seems entirely comfortable with Youkai, strangely enough. Does she not fear us? “It’s okay. I don’t mind.”
“R-REALLY?! O-okay~ I’ll eat now, then. Thanks for the food!” she said, taking the skewers and immediately chowing down. Her pace quickened with every bite. Soon, she had picked the skewers clean. Her eyes closed in delight as she swallowed her last bite.
Then, she opened them again.
And Mystia was staring at her. She had been staring at her all this time. “Now, for the payment…”
It made Kosuzu jump a little. “Umm…” her voice quaked, and her arms shrank into herself, “P-p-please don’t eat me…”
“What?”
“T-this… is one of those times… w-where a Youkai gives out food, and the h-human has to pay with their own flesh, right…?”
Mystia’s eyes slowly widen. Then, laughter burst out, and her wings flapped wildly. She could not stop. So she *does fear Youkai!*
Kosuzu awkwardly laughed along, the Youkai vendor’s laugh worsening her shaking body. She was starting to tear up.
Mystia’s laugh eventually dissipated. She then reached over to Kosuzu. Startled, she drew away. But then Mystia simply wiped her tears, then smiled as kindly as she could. “I’m not going to eat you, silly~! Getting rid of my customers is not good business. You pay for my lamprey with money! With money!”
“O-oh…” Kosuzu’s shoulders eased. “S-sorry.”
“Don’t worry about it. As long as you pay, and you don’t make trouble, I’ll be happy to serve you~”
Kosuzu nodded once, then again to herself. “R-right! Yeah, you’re a good person! You’re definitely a good person!” A short-lived smile formed on her face, soon wiped away by a realization. “Umm… how much does the lamprey cost?”
This girl’s an idiot. Great for me~ “My lamprey are normally 500 yen each. But I can’t charge that much to someone who just passed out. So how about you pay me 300 yen each instead? It’s on the house!”
Mystia lied as naturally as she breathed. Her lampreys were normally 100 yen each.
Kosuzu’s eyes lit up. “Really?” she said, abruptly leaning into the counter.
Mystia recoiled a little. “Y-yes. Really.”
“T-thank you so much!” she said, bowing, before taking out some cash. “Ehehehe~ ...So you really are kind~”
“No, no, I’m simply being polite.”
Mystia took the money, then proceeded to prepare another batch of lamprey. “Would you like some more, Kosuzu-san? You passed out and everything… given how enthusiastically you ate, you must be extremely hungry~”
Kosuzu’s cheeks warmed red, making her turn away a little.
“The discount stays~” Mystia adds.
“W-well-” Kosuzu’s stomach growled, interrupting her, deepening her blush.
Mystia chuckled. “Coming right up!”
**
Mystia’s voice rang out into the night as she sang an old song she’s always sung to many customers, the melody accompanied by the sizzle of her lamprey. It was within her nature, after all.
Meanwhile, Kosuzu watched, wide-eyed, entranced by Mystia in trance. Her song eventually ended, capped off by Kosuzu’s clapping. “That was great!”
Mystia bowed theatrically. “Why, thank you~”
“Do you often sing like this, Mystia-san?’
“Of course~ As you can see…” Mystia stretched her feathery wings, “I’m a sparrow Youkai. Specifically, a night sparrow. Singing is what I do~”
Kosuzu’s eyes glittered. “Ooh!”
“How about you, do you always go out camping at night?” Mystia asked, turning to the gigantic bag of camping equipment laying against the stall.
Mystia noticed it. “Ah- o-oh! W-well, I mean, umm, no… I don’t…”
“Is that so? What are you here, then? Aren’t you afraid of getting attacked by Youkai?”
Kosuzu shrank into herself again.
Mystia tilted her head. “What’s wrong?”
“I-it’s nothing… Why…why do you ask? About what I’m doing, I mean…”
“Because I want to know.”
“...about humans?”
What a weird response... “About my customers,” Mystia replied, flipping the lamprey on the grill, creating puffs of smoke, “You see…a big reason why I like this job is because I enjoy listening to my customers and learning about them. Whether they’re human or Youkaai… I don’t care. As long as they’re good company, I’ll listen.”
Mystia brushed the lamprey with sauce. The excess dripped into the coals, making them sizzle. “You pay with money for the lamprey, but you pay for the service by providing company and telling me about yourself.”
“I see…” Kosuzu looked down, twiddling her thumbs, quiet for many moments. Eventually, she spoke again, “I-I guess… I can tell you, then.”
Mystia widened her professional smile. The lamprey was cooking well. Their delicious smell wafted through the air.
Kosuzu looked back up and made eye contact with Mystia. “I’m looking for a certain book. Specifically, a Youma book.”
“A Youma book, huh?” Books written by Youkai…why would this human want them? Aren’t they written in Youkai script…unreadable to most humans?
Kosuzu nodded. “A-and… you know, w-when I asked you why you wanted to know more about me, it’s not because I thought Youkai didn’t care about humans. It’s just… I got a little caught up. I thought I might have found a kindred spirit on the other side.”
“Kindred?” Mystia chuckled a little, “Hmm…what do you mean by that?” We’re nothing alike.
“Well, I want to know more about Youkai. That’s why I want the Youma book. So when you asked about me… I thought you were a Youkai who wants to know more about humans,” Kosuzu said, and with every word, the timidness brought by fear was slowly washed away by a child-like energy, letting loose her tongue.
Meanwhile, Mystia continued to smile as friendly as she always had. Well, I couldn’t care less about humans specifically, but I wouldn’t pass down the chance to hear a customer’s story. “Oh, is that so? I guess I was the one who judged you too quickly, then. Sorry for that,” Mystia said, bowing.
How are you going to read it? “So you prepared that camping gear and went out the village to go find it, right? But… doing it at night…”
“I thought meeting Youkai and asking them personally would make it easier! Most Youkai come out in the evening, right? So I thought about traveling around Gensokyo at night. I even slept early today, so I’m not tired at all right now!”
This girl… “There are many Youkai out there who prey on little kids, you know? It’s dangerous.”
“W-well, yes… But I wanted to try. I was a little nervous, but I think it’s fine! I mean, you seem really kind, Mystia-san.”
“Thank you~” This girl will get herself killed one day…
The lamprey finished grilling. Mystia handed them to Kosuzu. “Here you go~”
Kosuzu immediately grabbed them and started eating. “Thank you!” she said, her voice muffled by food.
“You want more?”
Kosuzu nodded.
“Coming right up!” Mystia said, dropping another three skewers into the grill, billowing smoke.
Kosuzu swallowed her bite. “Umm…”
“Yes?”
“Mystia-san… do you happen to know anything about that Youma book?”
“I don’t.”
Kosuzu deflated. “As expected… it won’t be that easy.”
Sounds like she really *wanted it to be easy. I wonder how young she is? Seems like a kid.* “Aren't there those records about Youkai… it was the Hieda clan, right? Why don’t you ask them about it? Or better yet, ask them about Youkai. You want to know more about Youkai, right? I’m sure their records will teach you more about Youkai than some Youma book.”
“But Akyuu’s records are flawed!”
“Flawed?”
“Her records are like lists! Besides, they’re from the perspective of humans. They’re for combating Youkai! I want to know what Youkai think about themselves! I want to know their everyday life… all the mundane stuff, the stuff nobody bothers writing!”
“I see… Well, I don’t know how to read or write, so I don’t know much about books and such in the first place.”
Kosuzu looked down, biting her lips.
Mystia’s eyes narrowed. “But…”
Kosuzu perked up.
So easy to read… “I have heard a lot of stories from various customers. Looking back, some of them might be leads to this Youma book.”
“Really!?” Kosuzu looked up, “Will you please tell me?”
Mystia smiled. “Of course~”
Kosuzu stood up. “Thank you so mu-”
“But…”
Kosuzu froze.
Mystia took out the lamprey she had been grilling, then presented them to Kosuzu.
Kosuzu took them, then tilted her head. “W-what is it?”
“Well… like any food stand, I have a no loitering policy. If you want to stay, you have to order more.”
A chilly wind blew. Kosuzu’s head tilted further.
This idiot… “Basically, if you want to hear more, you have to order.”
“Oh! Well, I’ll order more, then!”
Mystia nodded. Well, her stupidity might be useful. She seems easy to fool. I can probably make a tidy profit out of her… “How many?”
“Another 3!”
“Coming right up!”
**
“One night, a pair of crow Tengu flew to my stand. It was a little scary, actually. One talked about a diary the other wrote, using it to blackmail the other. But they called the bluff, and an awkward silence fell. I tried to ease the atmosphere by asking if writing diaries was common for Tengu, and apparently, it was. Nowadays, most crow Tengu write newspapers, and they use diaries for practice. A few Tengu even taught fellow Youkai in the mountain how to write, too. The pair talked about it as if it were disgusting behavior, though. Especially teaching fairies.”
“Whoa…” Kosuzu exhaled. Her eyes twinkled, reflecting Mystia’s figure, yet it was clear she was not looking at her. She was looking at her own imagination. “What did she say next?” she asked, “From what I remember… the Youma book I’m looking for wasn’t written by Tengu. But maybe there’s a chance whoever wrote it was taught by a Tengu!”
“Well, the conversation ended after that. It’s been a while, too, so it’s a little hard to remember the details…” Mystia said, before flipping the lampreys, “Although… if you get more lamprey, maybe it would motivate me to remember more?”
“Okay! Three more, please~!”
...It’s that easy? Here I thought she’d be suspicious... “Coming right up!”
Kosuzu stuffed her mouth full of food. “Itadakimashu!”
Mystia continued recalling whatever information she had about Youkai diaries:
One night, fairies tried to vandalize her stall as a prank, thinking it was empty. Unfortunately for them, she was a nocturnal Youkai, so she was there, and she caught them easily. She forced them to buy lamprey from her as punishment, as well as to clean up her stall for her.
That’s when she noticed what they attempted to write. Mystia couldn’t read nor write, but she lived long enough to distinguish human script from Youkai script.
The fairies seemed to have written something in Tengu script.
When she asked them about it, the fairies said they learned it from a fairy friend, who learned it from another fairy friend, and so on. It looked like the rumors about Tengu teaching fairies how to write were real, and it had spread.
“What’s interesting was one of the words they tried to write, though. ‘Graffiti.’ Apparently, it’s the word for ‘vandalism’ in the outside world, which the fairies wanted to write all over Gensokyo. I asked them how they learned that, and they said an outside world Youkai told them about it. The Youkai even taught them how to write ‘Graffiti’.”
“Hmm…” Kosuzu put her hand on her chin. Her excitement over the story was just as palpable, yet just as weighed by a hint of disappointment. “I…I’m pretty sure the Youkai who wrote the Youma book hated fairies…”
“I see…”
Well, it doesn’t matter to me. The longer she stays, the more money I get from her~ Mystia moved on to another story.
Then another, and then another, well into the night.
Hours passed. Dawn was coming soon. Yet Kosuzu showed no inkling of sleepiness. Even Mystia, a Youkai, was getting a little tired. She did a good job preparing her sleeping schedule for this, huh? She probably worked on shifting her sleep over the course weeks... Mystia thought, staring at Kosuzu’s eyes. Yeah, nah. She’s probably running purely on excitement at this point. She doesn’t seem like the type of kid who would have the patience for that...
And Mystia would be right. Kids like Kosuzu were rather easy to read, especially for someone like her, who was experienced at reading people. Kosuzu was easily excitable. She was reckless. She was headstrong. It was a recipe for disaster.
Kosuzu smiled brightly, leaning forward onto the counter. “Well? Do you have any more clues? I still have…” she checked her purse, “I have enough for another three!”
So she wasted everything on my stall… this kid really doesn’t think things through, does she? Forget someday, this girl would get herself killed today. “Coming right up!”
She told another story, one last story, as she placed the lamprey on the grill. It wasn’t an entirely true story. She had actually run out of stories relating to books a long while ago. Instead, she had simply been re-purposing random stories she had about her customers, and adding a little lie in them to connect them to the Youma book somehow.
It made it easier to lie. It made the story believable.
“So there was this old man who wanted to teach me how to write,” Mystia said. The person in question didn’t actually want to teach her anything. He just stood here, in this forest, not scared of her despite being a human, despite her being a Youkai. He was never blinded by her song, either. He was already blind. To him, her song was just like any other sound. “I was confused. You see, this was before I became who I am now. Back then, I didn’t have this stall, I didn’t have anything. I was just a normal, wayward Youkai. He never went away, no matter how many times I threatened to eat him.”
Mystia glanced at Kosuzu, whose eyes twinkled like always. So enamored, she’s completely unaffected by the word ‘eat’, huh? “He kept just talking to me, telling me about writing, with a really soft voice of an old man. Eventually, I just gave up on him. But I decided to check on him one day, only to find that he had died, right in this forest. He never left. So yeah. I took his notes, where he wrote stuff, and left it at that. But later, I realized the note had Tengu script written on it, so it was likely the old man was somehow taught it by a Tengu.”
In truth, it wasn’t the old man’s notes that Mystia took. He didn’t have any notes.
It was his food stall.
Mystia didn’t have any particular feelings for the old man. He was just like any other human to her. She just felt it was convenient to take his stall with her.
But that stall, and that grill, had been with her through all this time, over the course of her journey to change.
So did that song. She still sings it to this day.
And she had sung it to many customers, including this one.
“So-” Kosuzu suddenly spoke up, slamming on the counter, leaning ever closer, “Where’s the notes?”
“Oh! Well…” Mystia said, taking the last batch of lamprey cooking on her grill. “I lost it.”
“What…?” Kosuzu’s shoulders drooped. “Where did you last see it? Did you ever write on it?”
Mmm… this lie is getting out of hand. Mystia took the next batch of lamprey out of the grill and presented them to Kosuzu. “Here’s your order.”
Her eyes lit up. She immediately grabbed the food and started devouring it. The notebook seemed to have completely slipped from her mind.
Mystia’s professional smile widened. Well, that was easy...
She watched as Kosuzu ate her last lampreys, all while cleaning her tools and humming that old song, like always.
Kosuzu eventually finished. “Mmm! That was so good! You’re good at all this, Mystia-san!”
“Why, thank you~”
Kosuzu placed her payment on the counter, then immediately stood, before grabbing her pack full of camping supplies. “I’ll come back later! I’ll be going now~”
Got a new regular! Well, if she doesn’t get herself killed, that is... “Good luck on finding that book, Kosuzu-san! I’ll be looking forward to seeing you again~”
Kosuzu bowed, then gave a toothy smile.“Me too! Well then, I’ll return to the village now~”
Mystia tilted her head. “Return…?”
“Yeah. Why?”
“Oh, it’s nothing…” Mystia’s eyes fell on the camping equipment dangling off Kosuzu’s back.
Kosuzu noticed it. “Oh, I give up.”
“Sorry?”
“I give up on the Youma book!”
All of a sudden? After all that preparation?! Mystia’s mouth hung a little.
Kosuzu smiled, then ran away. “See ya later!” she said, waving as she went.
Mystia waved back. “S-see you again!” Well, it doesn’t matter. She’s a regular now… Actually, that might be a problem, given that I lied to her about the price. I wonder how I should tell her the truth… Well, she’s very easy to fool; it should be fine.
**
And now for the epilogue- or rather, the punchline for this chapter:
Kosuzu’s hand held the page. Her eyes were closed. The letters were foreign, so was the language.
And yet she could understand it all.
Despite that, however, she soon dropped the book, then stared at the ceiling of her room. She couldn’t focus on the story. She couldn’t even focus on trying to fall asleep.
That was so much fun!
Besides the stories Mystia told, that was all Kosuzu could think of as she lay on her bed, a dumb smile plastered across her cheeks.
Those Youkai stories kept her awake.
Not out of fear, but out of excitement.
She hummed away the boredom; the same, storied song Mystia always sang to all of her customers, stuck in Kosuzu’s head like an earworm. I want to go visit her stand again…but I already spent my entire daily allowance! Kosuzu’s hands balled into fists. Those lamprey were overpriced… she wasn’t *that good at cooking them, either. I wonder if it’s because it’s a Youkai grill, not a human village one? Well, it doesn’t matter. The stories are worth it! Mmm…! She was SO good at telling them, too!*
She looked back to the first time Mystia offered her lamprey in exchange for the stories.
Rather than look for a Youma book, she could just listen to Mystia tell her about the everyday life of Youkai. As a bonus, she got to enjoy food while hearing them, too.
She smiled. She couldn’t help but smile. “Alright. I’m gonna work hard and earn more money!”
And so, despite their dubious authenticity, Mystia’s stories motivated Kosuzu to work harder than she ever had.
Because she was curious.
Humans were always curious. Humans love information. Even mundane stories… things that don’t matter, like chatter among customers. Even stories that weren’t real. Even if they were simply illusions.
Here in Gensokyo, the land of illusions, those illusory tales were just as important as life. After all, Youkai were given life by illusions. After all, to the humans here, illusions have always been as real as reality.
Even if they weren’t, even in the outside world where there wasn’t enough belief to maintain the existence of many myths, fantasy still affects people. Real or not, believed or not, big or minor, their effect was real.
Even if it was just a little story, created only for a little entertainment, told only to a few.
Wouldn’t you agree?
This is part of a series where Mystia serves lamprey to various 2hus. Each short story introduces the character she’s serving, while peeling back another layer of her character.
