Chapter Text
Slime Breathing First Form: Leisurely Vacation
[Edited April 10, 2026]
Chapter 1: A Frozen Butterfly
After centuries of ruling as the supreme deity of an ever-growing multiversal empire, Rimuru Tempest was tired.
Not physically tired—because, well, he couldn’t really get tired anymore—but mentally and emotionally. Managing godhood, politics between different realms, and dimensions was draining, even with Ciel-san doing most of the heavy lifting.
So Rimuru did what any overworked person would do: took an indefinite leave without informing anyone. He knew his subordinates could manage without him; just to be safe, he left a copy of himself to help with the management. If another apocalypse were to happen, he would know. But for now, he was overdue for a vacation, and no one could stop him. Opening a portal, he started to wander through random realities, checking if there was something he could do to pass his boredom. And with that, the time passed by without Rimuru's notice.
He didn’t even remember how many worlds he’d passed through already. Most of them blurred together—some post-apocalyptic, some high fantasy, one or two with mechas. Then, without warning, as he stepped through another tear in dimensional space, he discovered something unexpected.
Rimuru landed softly, floating just above the ground in the middle of a shattered field. The ruins of a small town stretched out around him—broken lanterns, cracked roof tiles, and walls reduced to splinters. Blood stained the dirt, and the air still held the bitter tang of battle. Ciel, ever dutiful, instantly cast a layered concealment barrier around him as soon as they landed. His presence vanished from the world, even from the senses of the most spiritual beings.
Rimuru looked around, raising an eyebrow. “Hmm, what kind of world is this this time?”
[Atmospheric analysis complete, Master,] Ciel spoke calmly in his mind. [You’ve arrived in a reality consistent with Taisho-era Japan. Spiritual energy signatures detected.]
“Taisho-era?” Rimuru tilted his head, eyes narrowing. “Wait a second…”
From the far side of the field, the clash of metals rang through the air along with a breathless sound of desperate shouts, grunts, and pants. Rimuru turned his head just in time to catch the blur of two figures locked in battle.
A woman—beautiful and graceful, with a butterfly hairpin in her long ebony hair—darted through the battlefield. Her sword danced like petals in the wind, every movement a testament to years of hard training. Watching her take a deep breath and shift through elegant twists and twirls as she wielded her blade was breathtaking. However, it was clear she had been battling her opponent for hours already; she was beginning to struggle, while her opponent didn’t seem winded at all.
Rimuru’s eyes shifted to examine the girl’s opponent. It was a man with rainbow-colored eyes, a twisted grin, and the unmistakable kanji for “Upper Moon Two” etched into his irises. He laughed as frost crept from around him, turning the air and the ground beneath them to ice. He held a pair of sharp fans made entirely of shining gold, each engraved with a lotus design and adorned with a green tassel at the base—his primary weapons.
Rimuru blinked, then his eyes widened in realization.
“Ah!” he exclaimed, lightly thumping a fist into his open palm. “I remember this! I read and watched this one!”
[After rescanning Master's old memories, I confirmed that the title of the manga and anime is Kimetsu no Yaiba—also known as Demon Slayer,] Ciel said with a knowing sigh. [A notable fictional work from your first life. You nearly failed your college exams binge-watching it.]
“Ohh man, that’s right,” Rimuru muttered, conjuring a small stool beneath him as he plopped down. “Doma and… uh… the butterfly girl. What was her name again?”
[Kocho Kanae. Flower Hashira. Older sister of Kocho Shinobu. This encounter is a canon event—her final battle before her death.]
Rimuru's eyes narrowed behind his aura-concealing mask. “So I did land before the start of the main story, huh?”
[Confirmed. The Kamado family massacre is still a few years away.]
A slow grin spread across Rimuru’s face as he summoned a bowl of popcorn with a casual wave of his hand and a chair to sit on. “Well, well… talk about unexpected fan service.”
Rimuru sat cross-legged, munching popcorn as he watched the intense battle from a safe distance. “Man, this is just like those isekai self-inserts I used to read.”
The fight raged on, brutal and one-sided. Kanae’s movements grew sluggish. Frostbite crept along her limbs and definitely inside her lungs. Her breath was growing shallow. Rimuru’s expression darkened slightly.
“Doma’s just playing with her,” he muttered. “He could’ve ended this ages ago.”
[Would you like to intervene, Master?] Ciel asked, tone neutral.
Rimuru tilted his head. “I don’t know how the manga ended, remember? I died before finishing it.”
He continued chewing slowly, watching as Kanae collapsed to one knee, blood staining her uniform. Her lungs were beginning to freeze.
He sighed, shaking his head. “But I do remember she didn’t make it.”
[Then shall I prepare for battle?]
“Nah,” Rimuru said, eyes watching the sky. “He’s leaving.”
As the sun began to rise, the rainbow-eyed demon finally stepped back. Doma clicked his tongue in disappointment and gave a dramatic sigh.
“What a shame,” he said with a smile that made Rimuru’s eye twitch in mild annoyance. “I didn't notice the time. I wouldn't be able to eat such a beautiful lady like you. You could've rested better inside of me.”
With that, Doma vanished into the shadows, escaping the approaching daylight.
The moment the demon’s presence disappeared from the area, Rimuru stood up and walked across the quiet battlefield.
He knelt beside the broken body of Kocho Kanae—bloodied, frostbitten, breath shallow but still clinging to life by a thread.
She managed to open her eyes to look at him. Even through her beat-up body, she still managed to look alarmed at the unknown presence in front of her. "W-Who are you?"
Rimuru stared at her quietly for a second before he smiled, although she wouldn’t be able to see it since he was wearing a mask.
“Alright, time to break the plot,” he muttered. The lady looked confused, but she wasn't able to say anything as Rimuru devoured her whole.
[Void God Azathoth – Consume.]
Kanae’s body shimmered and vanished into Rimuru’s [stomach]. All her wounds were instantly healed. Her soul gently stabilized, placed into protective stasis. Her skills, breathing forms, and memories were instantly analyzed and copied.
[Restoration complete. She will awaken once her physical body is fully recovered,] Ciel confirmed.
“Good job, Ciel,” Rimuru said, stretching. “Tough luck, honestly. She didn’t deserve to go out like that.”
He would let Ciel handle her recovery while he decided his next course of action.
Rimuru stared at the morning sun before he pulled on a specific individual in his many connections inside his soul corridor.
He raised a finger—and space itself shimmered as a rift opened.
From the darkness stepped a familiar figure, dressed in a black butler outfit, a pleased smile plastered on his lips.
“Rimuru-sama,” Diablo greeted, dropping to one knee. “It’s been centuries since you called me. How may I serve you?”
“Yo, Diablo,” Rimuru grinned. “I just dropped into an interesting world. I’m planning to stay a while. Can you find me a place to crash?”
“Of course. I shall find you a location befitting your divine presence.”
Rimuru wanted to say that anywhere was fine as long as he could sleep, eat, and read peacefully without interruption, but he decided against it, knowing how his subordinate acted when it came to him.
He sighed. “Do whatever you want. Also, I want you to get intel, but make sure you won’t be detected. Everything about this world—the Demon Slayer Corps, the Upper Moons, this ‘Muzan’ guy, the state of Japan, the tech level, the food…”
Diablo bowed. “Consider it done, Rimuru-sama. As always, it is an honor to serve.”
“Yeah, yeah,” Rimuru said, chuckling. “You’re still the same.”
Diablo gave him a pleased smile, visibly vibrating as he tried and failed to contain his joy. Seriously, this guy.
As the demon vanished in a flash of black magicules, Rimuru stretched and turned his eyes to the distant mountains.
“Oh, and Ciel?”
[Yes, Master?]
“Ask my clone back in my original world to fetch the complete Demon Slayer manga. If it’s finished, I want to read it all.”
[Already in progress.]
Rimuru smiled.
This was the kind of vacation he’d been waiting for.
[To Be Continued…]