Chapter Text
Sanemi Shinazugawa's heart pounded in his chest as he sprinted toward the Butterfly Mansion, the wind whipping at his face. Shinobu’s crow had delivered the message- something about Genya, something bad. He hadn’t waited for the rest before he took off running.
It finally happened.
Sanemi had warned him. Pleaded with him to quit the Demon Slayer Corps before something like this happened. Genya had eaten demons before and always reverted back to normal, but this time- this time he wasn’t reverting.
Why didn’t he stop when I told him?
The fear gnawed at him. Would they have to kill him? Would they make him do it? The thought of having to raise his sword against his own brother made him sick. His only goal, the entire reason he joined the Corps, was to protect Genya. How could he have failed so completely?
The mansion loomed in front of him, and Sanemi barely registered the door before he slammed it open with a force that rattled the hinges. The sharp sound echoed down the hallway.
Inside the room, Shinobu stood with Aoi, Sumi, Kiyo, and Naho. But what drew his attention the most was the towering figure of Gyomei Himejima, standing with his broad back to the door, obscuring the view of the bed.
Sanemi’s breath caught. He stepped forward, expecting the worst- his brother, tied down, thrashing like a monster, the only solution being-
"Welcome, Sanemi," Gyomei's soft, rumbling voice broke through his panic, calm and grounded as always. The Stone Hashira moved aside, and Sanemi's heart nearly stopped when he saw what- or rather who- was in Gyomei's arms.
"Genya?" The name escaped his lips in disbelief.
His younger brother wasn't tied up. He wasn't rampaging. In fact, Genya was small- tiny, even. He looked as though he’d shrunk down to the size of a child, no older than when Sanemi had left their home village. Maybe even smaller than that.
But that wasn't the most jarring thing. Genya had cat ears. Actual, black-tufted, twitching cat ears, and a long tail that flicked around his oversized shirt.
What in the hell…?
To Shinobu's side Sumi held a cat toy, waving it cautiously, while Naho stood off to the side with an uneaten fish. Genya, nestled against Gyomei’s chest, flinched at the loud door slam but quickly relaxed as Gyomei gently soothed him.
Sanemi’s eyes widened as Genya squirmed in Gyomei's arms, his large eyes lighting up.
"Nemi!" he cried, wriggling free from the massive Hashira's hold and stumbling toward Sanemi as fast as his stubby legs could manage. His tail flicked excitedly behind him as he dashed forward, the scar still faint on his baby-like face.
Sanemi stared in shock as Genya barreled into him, his arms unable to reach fully around him as he nuzzled his face against Sanemi’s exposed chest with a giggle. His eyes were wide and bright, filled with pure, innocent excitement.
Shinobu's soft laughter broke the silence. "It seems he’s happy to see you," she said, amusement dancing in her eyes.
Sanemi stood frozen, his mind reeling. He was relieved but… what…what happened to him? What happened to his brother?
"He ate a bakeneko." Shinobu explained, as if sensing his unspoken question.
“A bakeneko?”
"A demon cat.”
“I know what a bakeneko is.” Sanemi snapped at Shinobu, and felt Genya flinch, his small hands curling into Sanemi’s top. Looking down and seeing his brother was fine, smiling the moment they made eye contact, he returned his gaze back to the insect hashira. “Those are real too now?
“Well, it was a demon that transformed into a cat with twin tails. We’ve seen demons transform before, but it is quite the transformation for even demon standards, don’t you think?”
“Mm-hm! And since it had twin tails it made sense to call it a bakeneko, right?”
Sanemi looked at both Shinobu and Kiyu as they spoke, then let out a grunt. “I don’t care what you call it- it’s a demon. What does that mean? Is he…” Sanemi gulped, not wanting to ask it outloud.
“This isn’t permanent, I believe- at least, he shows no interest in eating humans, and the sun doesn’t affect him. His skin looks the same under a microscope as before. He appears harmless right now, though… well… he’s rather attached to Sanemi-san, isn’t he? Ah, and as you can see, he’s taken on some feline traits."
"Feline…traits," Sanemi repeated, dumbfounded. His brother had become some sort of cat-boy-child hybrid?
Shinobu nodded. "I believe he’ll revert back eventually. It just might take some time. Oh, and his wounds healed up before he got here so, Genya probably also has his usual traits from when he’s eaten demons in the past."
Usual demon traits? Looks the same under a microscope?
Sanemi looked down at Genya who was still clinging to him, and at some point had started purring. Purring. His eyes were wide and sparkling with adoration as his tail swung back and fourth- as if his already adorable brother needed help being even cuter.
Sanemi sighed, dropping his hand onto Genya’s head, ruffling his fluffy hair- between the cat ears, of course. The little ears twitched at his touch, and Genya’s purring grew louder.
“Genya, what did you do?”
Genya tilted his head and Sanemi let out a slight sigh. It appeared the other didn’t understand him, or know how to answer.
"Idiot," Sanemi muttered under his breath, though his voice lacked the usual harshness. "I told you to quit."
Genya, oblivious to the scolding, simply gazed up at his brother, as if the mere sight of Sanemi was the best thing in the world.
"Nemi!" he said the one word again, same as before, happily.
Sanemi let out a long breath, feeling the tension drain from his body. He looked around the room, noting the concerned but amused expressions of the others present, along with the sizable amount of tears running down Gyomei’s cheeks.
"So… what happens now?"