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2025-10-18
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2025-10-22
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4/?
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the fate of the red string.

Summary:

Soulmates were precious—rarely found, and even more rarely understood. Those who did find theirs held on tightly. The red string of fate bound destinies together, bringing people to one another, unavoidably.

Sanemi and Sabito had found each other. The thread wrapped around their wrists—but that wasn’t all.

There was another name inscribed on both of their wrists.

Tomioka Giyuu.

Notes:

(See the end of the work for notes.)

Chapter 1

Chapter Text

In the past, demons were everywhere. They appeared before humans and slaughtered them. Then there were demon slayers and Hashira. They fought against demons and protected people. This went on for a long time. After the battle with Muzan, the leader of the demons, many things changed. Almost everyone died, and most of those who survived only lived to a certain age. In the end, no one from the demon slayers remained…

One hundred and fifty years later, when Japan entered the modern age, many of the dead were given a new chance — a chance to finally find the peace they deserved. In the world they awoke to, people were divided into three statuses: alpha, beta, and omega. Moreover, when they turned eighteen, the reincarnated would regain their memories, and those with soulmates would see their partners’ names on their wrists.

Obanai and Mitsuri were soulmates; after the promise they made in their previous lives, they were together once again. The moment they turned eighteen, they searched for and found each other. The entire group had slowly begun to reunite. Sanemi was with his brother this time. Of course, Genya did not remember yet because he was sixteen, but by coincidence, he went to the same high school as fourteen-year-old Muichiro.

Moreover, Sanemi also had a soulmate — Sabito. Since they were both alphas, they gave off a very strong impression. There was one thing the two of them shared in their pasts: Tomioka Giyuu.

Before Sabito died at an early age, he had told them that he and Giyuu had a pure, youthful relationship. Naturally, the group was surprised. Someone Giyuu had once spent time with was now among them again. Sanemi also mentioned that after everyone else died and only they were left, a small spark had formed between him and Giyuu. But both were too tired and broken to take it any further. In the end, Giyuu took his own life before even reaching the age of twenty-five.

When Sanemi told them this, they were all shocked — Mitsuri had cried. Sabito, on the other hand, had stayed silent for a while, and Sanemi had comforted him. Giyuu had always seemed depressed. It was understandable that he couldn’t endure anymore after everything that had happened. When Tengen and Sanemi found his lifeless body, it was already too late for everything. Since remembering his past, Tengen had blamed himself deeply for it.

And now, Tomioka Giyuu was nowhere to be found. He hadn’t tried to contact them or find them. In a way, that was normal. Before entering the Infinity Castle, no one had really spoken to Giyuu. Could the time they spent together after the war really have made up for that? They doubted it.

Maybe Tomioka Giyuu had decided to live a peaceful life far away from everyone else.

How wrong they were.

 

---

When Obanai and Mitsuri left the restaurant where they had eaten, they were walking back to campus for their next class. Obanai was so happy to finally be with Mitsuri, and he was also thankful that he was a little taller than his girlfriend — he didn’t want to deal with Sanemi’s teasing like in the past.

“Do you think Tomioka-san doesn’t want to see us?”

At his girlfriend’s question, Obanai sighed. He wasn’t sure himself. In fact, they didn’t even know if Giyuu was alive. It was hard to say anything for certain. And there was another matter.

“I’m not sure, Mitsuri. Maybe he hasn’t even been born yet. And even if he has, there’s a chance he doesn’t remember us.”

When he saw his girlfriend’s confused and curious look, Obanai began to explain. When he first realized they had been reborn, he had done a lot of research and had also considered the ideas that Sanemi and Tengen gave him. Giyuu hadn’t died because of the mark — he had taken his own life. Because of that, it was possible that he couldn’t remember his past.

“But isn’t that a good thing?”

Mitsuri had said that with a curious expression. Obanai hadn’t immediately understood what she meant.

“If Tomioka-san doesn’t remember his past, he can truly start fresh. If we meet him again, we can be friends without the shadows of the past — and be more careful this time.”

When he thought about it that way, she was right. Obanai and Sanemi had pushed Tomioka too hard in the past. They had thought he believed himself to be superior to them — but that wasn’t true. After Sabito’s death, Giyuu had said he never considered himself a real Hashira. They had learned all this from Sanemi and Tengen.

“Whether he remembers or not doesn’t matter. If he’s alive and our paths cross, I want to support Tomioka this time.”

After he said that, Mitsuri kissed him on the cheek, and Obanai blushed. Getting used to these kisses would be hard — not that he minded.

“I’m proud of you.”

And they kept walking together.

There was a high school about ten minutes away from campus. Genya, Muichiro, and the Kamado kids studied there. Now that their classes were over, students were running around everywhere. At that moment, Obanai’s attention was caught by a group in the corner. Four people seemed to be laughing while cornering someone.

Obanai frowned and started walking toward them, with Mitsuri following behind.

“Hey, it’s your birthday today, right? Come on, let us give you your birthday present.”

As the freezing February wind blew sharply around them, Obanai noticed that one of the boys was holding scissors.

“You’re a boy, pull yourself together. We’ll fix your hair. What, trying to act like a girl, you freak omega?”

Obanai clenched his teeth. A child being bullied because of his secondary gender and appearance — there was no way he could ignore that. Handing his bag to Mitsuri, he walked closer. He saw one of the bullies shove the boy against the wall and make him fall. The boy kept his head down, but the groan he let out showed that he was in pain.

“Hey, you damn brats! Get away from him right now!”

When the kids turned to him, they all stepped back in fear. Obanai’s mismatched eyes and stern face created an intimidating sight — and they definitely deserved to be scared.

“We were just having fun,” one of them stammered, but said nothing else before they all ran off.

Sighing, Obanai crouched down beside the boy and held out his hand.

“Are you okay?”

The boy nodded quickly, hesitating for a moment before taking Obanai’s hand. He didn’t know if he and Mitsuri were feeling the same thing, but he suddenly felt a protective instinct toward the boy. He had heard that this kind of bond was rare — sometimes, an alpha and omega pair could develop a parental instinct toward a young one.

“Thank you,” the boy said quietly.

When he finally lifted his head, Mitsuri gasped. Obanai felt the same way.
Tomioka Giyuu was standing right in front of them.

He looked younger than they remembered — which made sense, since he was a high school student now. His hair was still long, but this time tied into two small ponytails on each side. He looked quite adorable.

“Are you okay?” Mitsuri asked, trying to recover from her surprise.

Giyuu nodded and picked up the bag that had fallen to the ground. His blue eyes looked slightly red, as if he had been holding back tears.

“Yes, I’m fine. Thank you for your help.”

After bowing slightly, he averted his eyes and ran off.

Obanai watched him go, not sure what to feel. Tomioka Giyuu was alive.
He was living as a high school student, at a school very close to theirs — and he was being bullied.

Damn it. He had to tell the others immediately.

Chapter 2

Chapter Text

Giyuu Tomioka’s life had started out beautifully.
He had a loving family, and a wonderful older sister.
They were a small but happy family—until everything began to fall apart.

First, he lost his parents in a car accident.
He was only ten years old, left with his sister, who had just become an adult.
She was smart and hardworking, so she quit school to start working.
Giyuu always blamed himself for that; his sister had loved school, but couldn’t continue.
Because of that, he studied harder than anyone else—to make her proud.
He got through his grief thanks to her.

Even though life was difficult, they managed to build some stability.
At least for a few years… until that day.
A rainy day he would never forget.

His sister had rented a car, and they were driving to an amusement park outside the city.
It was Giyuu’s birthday, and the young omega had never expected such a surprise.
His sister had always been thoughtful and gentle—he wanted to be just like her someday.
But things changed… A car lost control in the rain, and they crashed.

On the day he turned fourteen, Giyuu lost his sister.
He was trapped inside the car with her lifeless body for hours.
He cried until his throat burned, begging her to wake up, but she never did.
He didn’t remember how he got to the hospital, only that his custody was later given to his uncle.
He was just fourteen.

After the accident, he suffered cluster headaches, and the seatbelt’s pressure had damaged his lungs.
He developed asthma and had to rely on painkillers to function.
Rain and thunder terrified him.
He came to hate birthdays.

School was another nightmare.
Bullying was constant.
He grew his hair long in memory of his sister—wanting to look a little like her.
But as a male omega, he was often ridiculed for it.

At home, he endured his uncle’s physical and emotional abuse.
At school, he endured his classmates.

That day was no different—
they’d nearly cut off his hair again.
He was terrified… until two college-aged men intervened.
They’d helped him.

For the first time since his sister, someone had reached out to him.
Hesitant but desperate, Giyuu took their hands.
Their presence felt safe—warm, grounding.
But overwhelmed with emotion, he muttered a shaky “thank you” and ran off.

By the time he reached home, his tears had dried on his cheeks.
His uncle wasn’t home.
As he went to his room, he felt a burning sensation on his wrist.
Frowning, he rolled up his sleeve—
and froze.

He had just turned eighteen that day,
but Giyuu had never thought he’d ever get a soulmate mark.
Who would want an omega like him, anyway?

And yet… there weren’t one, but two names carved into his skin.

Shinazugawa Sanemi and Sabito.

It was rare, but possible—two people sharing the same bond.
He swallowed hard.
Would they even want him?
The thought seemed impossible.

As he stumbled into his room, his phone buzzed with notifications.
He frowned—he didn’t have friends, so who could be texting him?
Curious, he checked the screen and saw a message from an unknown number.

When he opened it, his heart nearly stopped.

Two photos.
Both of him.
The first one had been taken from outside his classroom window; he sat near the glass on the first floor.
The second was of him leaving school.
Beneath the photos was just one message:

“You’re beautiful.”

Giyuu swallowed hard.
What was happening?

 

---

Meanwhile...

Sanemi and Sabito were a good couple—
sharing the same interests, loving sports and cooking together.
Both were alphas, strong and confident.
Their similar pasts had brought them closer.
At university, they were admired—and envied.
After all, they were soulmates.

“Another love letter for you,” Sabito said, tossing a pink envelope on the table.

Sanemi rolled his eyes while Sabito grunted and threw the letter straight into the trash bin.
Seriously, why would anyone send a love letter to someone already taken?

“These idiots are hopeless,” Sanemi muttered.

“Exactly,” Sabito smirked, unwrapping his lunch.

Sanemi slid a sandwich across the table. “Eat. You didn’t have breakfast.”

“You’re the best boyfriend ever,” Sabito grinned, leaning over to peck his cheek.

A loud gagging sound came from behind them.
Sanemi sighed, turning to glare at Tengen Uzui, who was now sitting down with Rengoku.

“There are families here, man!” Tengen teased.

“Shut up, Tengen. Don’t be jealous just because you don’t have a boyfriend,” Sanemi shot back, flipping him off.

Sabito burst out laughing and high-fived him.
Rengoku just smiled, sipping his coffee calmly.

“Obanai and Mitsuri are late,” he noted.

“They’re coming,” Sabito said, pointing toward the courtyard.

Both of them looked… startled.
Something had clearly happened.

Sanemi was about to ask what was wrong when a sharp burning pain spread through his wrist.
He gasped, glancing down—and saw Sabito doing the same.

Their soulmate marks were glowing.
Their names had always been there, etched in red—
but now a third name was forming beneath them.

Tomioka Giyuu.

“Holy shit!” Sanemi and Sabito yelled in unison, staring at each other.

Giyuu was alive.
And not just alive—he was their soulmate.
Both of them.

“What are the odds of that…?” Sabito whispered.

Obanai’s voice broke the silence.
“We saw him. The kid. Black hair, blue eyes. He’s in high school now.”

They froze.

Giyuu was alive—living as a senior, completely unaware of them.

Sanemi’s voice was firm when he finally spoke:
“We have to see him.”

But tomorrow was the weekend.

Chapter 3

Chapter Text

Giyuu was tense — very tense. All weekend, he’d been thinking about his soulmates and the mysterious number that had texted him. He had asked who it was, but when no reply came, he’d blocked the number. Still, that hadn’t helped, because that morning, just as he’d entered the school, a photo of him had arrived from another number.

He had spent the whole day shut inside his classroom. It hadn’t been a problem since he usually brought his lunch from home. When no one was around, his eyes kept wandering to the names written on his wrist. Giyuu didn’t know what to do. There weren’t one but two names. How was that even possible?

“Hey, loser, you don’t even have a soulmate, do you?”

As the final bell rang, Giyuu quietly put on his coat and didn’t respond to the voice calling out to him. Nothing was certain yet, and he had no intention of revealing that he even had soulmates.

“Of course he doesn’t! Who’d ever want an ugly omega like him?”

Laughter erupted around the classroom. Giyuu swallowed hard. Ugly? His eyes flicked to his reflection in the window. His skin was pale and flawless, his height was what one would expect from an omega, and he was slender. His lapis-blue eyes, straight nose, and soft pink lips — they weren’t bad features. Maybe it was his hair? But Giyuu liked his hair. Was he really ugly? What would his soulmates think of him? Maybe it was better if he never met them at all.

“He’ll probably seduce some old alpha and steal his money.”

That was the last straw. Giyuu grabbed his bag and rushed out of the classroom. That’s not who I am! He just wanted to graduate and get into university. There were only four months left until exams. While everyone else was focused on him, he was focused on studying. It was ridiculous.

Sighing, he stepped out of the school building and headed toward the gate. He could go home, study, and wallow in his own misery — a perfect plan, really.

“Hey, hi there!”

He blinked in surprise when a young woman waved and called out to him. When he looked more closely, he recognized her — and the man beside her. They were the pair who had helped him before. Behind them stood four more people: one with white hair, another with peach-colored hair, one gray-haired, and another with bright orange locks streaked with red. Giyuu couldn’t help but notice they all had long hair. Didn’t they get criticized for that? Then again, it was clear they were all alphas.

“Um… hello?”

Why were they here? They almost looked like they’d been waiting for him. Giyuu didn’t understand.

“After what happened last time, we wanted to check on you. Are you okay?”

This time it was the black-haired one speaking. Giyuu found himself nodding. He was used to bullying — unfortunately. Even if he wasn’t okay, he felt like he had to say he was.

“Yes… Thank you for helping me. And for checking up on me, too.”

He spoke politely, and the pink-haired girl laughed brightly before stepping closer. Giyuu had to fight the urge to flinch.

“You’re so cute! I’m Mitsuri Kanroji — and this is my boyfriend, Iguro Obanai.”

So that was their names. Giyuu nodded slowly, careful not to meet the curious gazes of the others.

“It’s nice to meet you. I’m Tomioka Giyuu.”

Kanroji-san laughed again, her cheerful tone making him feel oddly unsettled. She seemed full of energy, like she was about to say something more. Just then, a garbage truck passed by, and Giyuu wrinkled his nose.

“Ugh, it smells awful!”

The young woman’s complaint matched his own thoughts perfectly. Then, to his surprise, Kanroji-san pulled a deodorant spray from her bag. Before Giyuu could move away, she started spraying it — right toward him. His bad luck was that the wind picked up at the same moment. The mist hit his face directly, filling his nose and mouth.

Giyuu felt his throat begin to burn, and he started coughing violently, hand clutching his chest as he bent forward.

“Giyuu-kun?”

He couldn’t breathe. Desperately, he reached into his bag — his inhaler had to be in there somewhere. He hadn’t had an asthma attack in a while, but this one was bad. Really bad.

“He’s having an attack!”

He heard a voice he didn’t recognize, but everything was fading. Then, his bag was pulled from his hands, and seconds later, something familiar was pressed to his lips. Eyes squeezed shut, he inhaled the medicine several times. The relief was faint — his body was trembling, drained.

“Hey, Giyuu?”

Someone was calling to him. Through half-open eyes, he saw two faces hovering over him — one white-haired, the other with peach-colored locks. Someone was crying. He wanted to respond, but his voice wouldn’t come. His vision dimmed, his body shaking where he stood, until he felt himself being lifted into strong arms.

“We’re taking him to our place. We can’t just leave him like this.”

He thought that voice belonged to Iguro-san… but he couldn’t be sure. His consciousness slipped away before he could figure it out.

Giyuu had never imagined his day would end like this.
It was strange — so very strange.

Chapter 4

Chapter Text

When they brought Giyuu to the house where Obanai and Mitsuri were staying, they took off his coat and shoes and laid him down on the couple’s bed. His breathing was steadier and more regular now, but Mitsuri, in particular, was terrified and kept crying. Of course, Obanai did everything he could to calm his lover. It took him a few minutes, but once she finally relaxed, they all moved to the living room.

“This isn’t your fault, Mitsuri... You couldn’t have known Giyuu was in that condition.”

As Sabito spoke, Obanai nodded, holding Mitsuri’s hand and letting her rest her head on his shoulder.

“Sabito’s right, don’t blame yourself. I’m sure Giyuu will understand too.”

Everyone was eager to see Giyuu, but it seemed it would have to wait a few more hours. When Obanai looked at the couple sitting on the couch, he tilted his head slightly — both of them were staring at the names written on their wrists. It must still have been such a strange thing for them to process.

“Man... After all we’ve been through, after finally getting better lives, why does Giyuu have to live like this?”

What Tengen said reflected what everyone was thinking. He was younger than all of them, bullied, struggling with asthma — and Obanai suspected there were many other problems too. He hoped he was wrong... what they already knew was bad enough.

“I’m going to destroy those kids at that school.”

Hearing Sanemi’s angry voice, Obanai couldn’t help but smile slightly. His friend had become more protective, more genuine, and more caring lately. Ever since he started dating Sabito, they’d both been like that — toward each other and everyone around them. Giyuu’s reappearance had clearly excited them both. Obanai shook his head lightly. They would make good alphas for Giyuu; otherwise, he’d have to scold them harshly.

After a few hours, Obanai went back to check on the young omega. When he entered the room, he saw that Giyuu was sitting up in bed, trying to make sense of where he was. Closing the door behind him, he walked closer.

“Giyuu?”

Startled by his voice, Giyuu flinched, then turned toward him with wide blue eyes. Obanai was still surprised by how expressive he had become — he hadn’t been like that in the past. But that was behind them now. This Giyuu was different, and so was he. All of them were.

“Iguro-san?”

Hearing the boy’s uncertain voice, Obanai smiled softly and sat down on the edge of the bed. The young omega was watching him carefully.

“Yes, it’s me. How do you feel? You passed out from an asthma attack.”

At his words, Giyuu grimaced, placing a hand on his chest and rubbing it gently — clearly a reflexive movement.

“I’m fine... it must have been too strong, so I lost consciousness. I’m sorry for troubling you.”

He truly looked apologetic, which surprised the alpha. There was nothing to apologize for. It was an accident, and since Giyuu was fine now, nothing else mattered.

“Don’t apologize. Mitsuri feels really bad about it and will probably hug you while crying and apologizing.”

That seemed to fluster Giyuu. He clearly thought there was no reason for anyone to apologize.

“But Kanroji-san couldn’t have known this would happen. I don’t blame her, really.”

His hurried tone made Obanai smile as he slowly raised a hand and gently patted Giyuu’s head, ruffling his hair. It was a completely instinctive gesture, and Giyuu looked surprised. His cheeks turned pink, and he blinked a few times.

“Those kids at school are still bothering you, aren’t they?”

When Giyuu averted his gaze to the wall, Obanai got his answer. It made his blood boil, but now wasn’t the time to bring it up.

“It’s fine... school will be over in a few months anyway.”

He sounded completely focused on that thought — but that was wrong. He was probably lonely and hurt. Obanai made a mental note to talk about it later.

“Do you have any friends?”

He was genuinely curious — having at least a few friends would be good for Giyuu. Talking to someone always helped.

“Not really... sometimes I talk with Tanjiro from the lower grades. And there’s Murata, who works at the stationery shop across from the school. I talk with them occasionally.”

It figured — Tanjiro always seemed drawn to Giyuu, no matter the world. Obanai wasn’t surprised at all. The boy was practically sunlight itself.

“I see. Come on, let’s eat. I should introduce you to the others too.”

Giyuu looked like he wanted to protest, but Obanai had already started walking toward the door, so he had no choice but to follow. As expected, the moment they entered the living room, Mitsuri threw her arms around Giyuu and began crying apologies. She spoke so fast that Giyuu couldn’t get a word in for several minutes. Eventually, Mitsuri calmed down a little.

“I’m so sorry, Giyuu-kun! You went through such a hard time because of me!”

When Mitsuri spoke, Giyuu shook his head and gave a small smile. To Obanai, that smile suited him. Out of the corner of his eye, he noticed Sanemi and Sabito watching Giyuu with visible admiration. They were definitely impressed.

“I’m really fine, Kanroji-san. You didn’t do it on purpose, after all.”

Watching his lover hug Giyuu again and gush about how sweet and kind he was, Obanai sighed and nudged Sanemi, who was standing beside him. It was probably time for them to make their move, wasn’t it? Thankfully, Sanemi got the hint and stepped forward with Sabito. Giyuu’s curious gaze followed them.

“We haven’t met before, Giyuu... I’m Shinazugawa Sanemi, and this is my boyfriend, Sabito.”

The moment Sanemi said their names, Giyuu’s eyes widened, and his hand flew to his right arm — the one where soulmates’ names appeared. Seeing the two of them in front of him must have been shocking.

“You...”

Giyuu’s voice trembled with surprise, and both alphas extended their arms. On each of their wrists, the same name was written: Tomioka Giyuu. Watching Giyuu slowly realize what it meant — and blush in embarrassment — was undeniably endearing.

“Yes,” Sanemi said softly. “We’re your soulmates.”

Even if Giyuu didn’t remember his past, he was once again reunited with the two men he had loved before. Obanai thought to himself that Giyuu was probably the luckiest of them all.

Notes:

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