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The problem started with the rice.
Inosuke Hashibira, King of the Mountains, had just been released from bedrest, a tedious and insulting confinement following his latest fight. His muscles felt slack, his joints felt stiff, and the silence of the Butterfly Mansion was an unending, infuriating pressure against his hyper-sensitive hearing. The only thing that made the confinement tolerable was the routine, and right now, the rice was wrong. It was too bland, too soft, and far too neat.
He stabbed the bowl with his chopsticks. “Hey, you! This mush tastes like dirt! Where’s the normal pig slop? Where’s the flavor that makes the air crackle?”
Aoi Kanzaki, who had been setting down a tray, paused and pinched the bridge of her nose. Her twin-tailed hair, tied with white butterflies, bobbed slightly. “It is not ‘slop,’ Inosuke-san. It’s nourishing congee for recovery. And I made it the same way I always make it for you,” she stated, her voice sharp enough to carve wood. “If you want to return to duty faster, you will eat it. Stop complaining. Some of our Demon Slayers have injuries far worse than yours, you reckless oaf!”
Inosuke felt the usual surge of competitive rage—the desire to shout louder, leap higher, and generally prove that he, Gonpachiro’s boss, was superior. He roared, slapping his hand on the table, rattling the bowls.
“Do not call me an oaf, you flat-faced wench! I am the Great Inosuke, and my slop needs to be cooked by the best!”
Aoi, however, didn't flinch. She simply fixed him with an icy blue glare. “I am not paid to be entertained by your tantrums. If you refuse to eat, then you will starve, and I will report you to Shinobu-sama. You’ll be in bed for another two weeks.” She turned and stalked away, her footsteps echoing sharply on the polished wood.
Inosuke stared after her, chest heaving. He expected the usual lingering anger, the satisfaction of winning a shouting match. But as he looked at the bowl of bland rice, he realized something strange. The anger was already gone. Instead, there was a hollow, annoying absence, like a challenging, strong scent that had just been yanked away.
Hah. She’s strong. Her shouting makes my skin tingle. It’s like a battle horn. He dismissed the feeling, attributing it to the strength of the person he had just "fought."
The true trouble began a week later, just as Inosuke was moving from simple massage recovery to the reflex training games. He noticed Aoi wasn't around. He didn’t care. Why would the King of the Mountains care about a noisy girl who kept trying to force him to take bitter medicine? He certainly didn't care that the mansion felt quieter, or that the food tasted even duller than before.
Tanjiro was the one who explained. “Aoi-san has been called away to assist with a complicated emergency. Someone was poisoned badly, and only Aoi-san knows the formula for the antidote, so she had to deliver it in person and monitor the treatment.”
Inosuke snorted from under his mask. “Hah! Running away from the Great Inosuke's training. Coward! She knew she couldn't beat me at the reflex game, so she flew off like a scared pigeon!”
But the reflex training was boring. The little girls, Kiyo, Sumi, and Naho, were too easy to beat, giggling as they ran. Even Kanao, with her overwhelming speed, was predictable. There was no spark. In the past, Aoi was the one who made the training worth it. She would shout, scold, and glare with a heat that Inosuke found thrilling. He realized he didn't enjoy beating Kanao or the little girls as much as he enjoyed winning in the face of Aoi's irritation. Her fierce disapproval was somehow more satisfying than praise.
He started trying to recreate the feeling. He tried shouting at Zenitsu, but Zenitsu just cried and whined, which was too pathetic. He tried challenging Tanjiro, but Tanjiro just looked at him with gentle, confused concern, which was like fighting a soft blanket.
It wasn’t right. The tension, the perfect thrumming of annoyance that settled deep in his chest, was missing.
One evening, staring up at the moon, Inosuke tore off his boar mask, confused and frustrated. He was the strongest, yet something was beating him. This hollow, itchy feeling was a new opponent. He closed his eyes and tried to remember the feeling of Aoi’s presence. He focused his acute sense of touch, the one that let him detect vibrations in the air and sense intentions. He remembered her specific shout: not just loud, but possessing a sharp, high frequency that was irritating and focused, like a perfectly thrown dart. He remembered the precise pressure of her hand when she forced the medicine into his grasp, a fleeting touch that was firm and non-negotiable. He remembered the smell—not the perfume of the wisteria or the disinfectant, but the clean, herbal scent of her clothes mixed with the faint, comforting smell of healing salve.
His mind suddenly clicked everything together, interpreting these sensory details in the only way his mind knew how: in terms of strength and ownership. This feeling, he thought, gripping his fists. This buzzing, wacky, challenging feeling… it only happens when she is near.
It wasn't a standard, mushy emotion. It was a unique, powerful phenomenon that belonged to him. It was a new type of hunger, a compulsion that demanded her presence just as he demanded to fight Upper Moons. He didn't want to fight her, exactly, but he wanted to feel her strength—her irritation, her presence, her specific, noisy existence—directed entirely at him. He needed her to be there to make the air crackle. This must be what it meant to find the strongest opponent. No, not an opponent.
The strongest annoyance.
The feeling, which he now recognized as desire for her presence, was so strong and singular that he had to categorize it. It was his new, personal phenomenon. It was his thing. He decided that this meant she belonged to his domain, just like his dual blades and his boar mask.
Three weeks later, Aoi returned. Inosuke knew she was back before anyone else. As she stepped over the threshold of the mansion, talking briskly to Shinobu’s other assistants, Inosuke felt the air change. The silence that had plagued him for weeks suddenly shattered, replaced by that familiar, annoying, and yet intensely satisfying thrumming in his chest.
She walked past his room on the way to the kitchen, her expression drawn from exhaustion but still taut with her usual stern focus. Inosuke dropped his practice sword with a clatter. He charged out of the room, running directly at her. Aoi stopped dead, her eyes widening. She braced herself, ready to receive a tackle or a challenge.
“Inosuke-san! What in the world are you doing? I’m exhausted! Go back to your room!” she barked, her voice already high and sharp.
Inosuke stood a foot away from her, towering in his mask. He didn’t shout. Instead, he jabbed a gloved finger right at her chest. “Oi, flat-face,” he growled, his voice low and intense. “You ran away.”
“I did not run away, you imbecile! I was on a mission! An important one! Unlike you, I actually contribute!”
“No, you flew off like a scared pigeon,” Inosuke insisted, slightly tilting his head. “And when you’re not here, the air is dull. The rice is soft. The training is boring. Don't you dare do that again, you hear me, woman?” He paused, trying to articulate the complex feeling of possessiveness, annoyance, and attraction in a way that made sense to his boar-brain.
“The unique, annoying noise you make… it belongs here. With the Great Inosuke. It is mine.”
Aoi stared at him, completely thrown off. She was ready for a fight, a chase, or a tantrum, but not this strange, demanding statement of personal ownership. Her face flushed a deep red that had nothing to do with anger. “Are you… are you trying to claim me, Inosuke-san? Is this some sort of boar mating ritual?” she demanded, her voice wavering slightly with confusion.
Inosuke just huffed, giving her a small, almost imperceptible nod of the boar mask. “Yeah. That. Don’t fly off again, Aoi,” he used her name, spitting it out with the weight of a newly discovered prize. “Now, make me the strong slop that makes the air crackle, or I’ll challenge that boar mask right off your head!”
He turned, feeling the perfect, familiar, infuriated thrumming of her presence behind him. The air was no longer dull. The King of the Mountains had found his treasure, and it was loud, strict, and very, very annoyed.