(What if everything follows canon after On the Flip Side chapter 12?)
This is an AU of On the Flip Side after chapter 12, where everything more or less follows canon. That is, Tanjirou was not present when Muzan paid a visit to the Kamado residence and killed everyone but Nezuko, who was turned into a demon. The story begins right after Tanjirou's first encounter with the Hashiras. Specifically, during his recuperation in the Butterfly Mansion.
This story is unbeta-ed. Forgive me if you see any glaring mistake.
If you haven't read On the Flip Side, please read it first (at least until chapter 12). Otherwise there will be many scenes that may confuse you.
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His heart skipped a beat when he caught a familiar scent of sweet wisteria.
Tanjirou looked around. The Butterfly Mansion was massive, bigger than the Fuji family estate he had been to a few weeks ago. The medical wards seemed to be able to house more than a hundred people. Butterflies floated around him as various scents wafted through his nose, some were faint while others more fresh.
But even amidst the sea of unique Demon Slayers' scents, he immediately caught hers the moment they stepped into the compound.
Flowers and spring, with a touch of rust. Still fresh, as if she was standing here just a moment ago.
Tanjirou wanted to follow her scent, but the Kakushi yanked his arm the moment he veered off of the direction they were going.
"You are injured. You could barely walk unassisted," the Kakushi scolded him, poking his side lightly. Tanjirou groaned in pain. "Plus, Kochou-sama is waiting for you. Agatsuma Zenitsu, Murata Jun and Hashibira Inosuke have been tended to; you're the last one. Explore later when you're in a better state."
"... Is Tsuyuri Kanao here?" Tanjirou wheezed.
"Tsuyuri-sama?" the Kakushi looked at him in surprise. "She's usually in the backyard, training."
"Can we go there?" Tanjirou asked. Shrunk back when the kakushi glared at him. "I-I mean, after we meet Kochou-san."
"And plenty of rest," the Kakushi added for him. Eyed him suspiciously. "I thought this is the first time you've been to Butterfly Mansion. How do you know Tsuyuri-sama?"
A crow's call. A ping of a flipped coin. A sweet smile, amidst excited little children and his mother's warm embrace. A piece of memory that reminded him of home. Of the peaceful times and bright future, back before everything went wrong—
"She's my friend," Tanjirou decided to say and smiled, before the image of his red red blood family could drown him.
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"It's been awhile, Kochou-san."
"It's been three years indeed," Shinobu smiled at the young man entering the examination room. "Though we actually met just a few hours ago, Tanjirou-kun. Remember the Hashira meeting?"
Tanjirou scratched his head sheepishly. Winced, when he accidentally scratched a head wound. Shinobu chuckled before gesturing for him to sit on the bed. He followed her instructions obediently, so unlike the two who came before him.
"...Thank you very much for defending Nezuko," Tanjirou said as she checked on his injuries. "I wouldn't know what to do without you being there."
"You're welcome," Shinobu hummed, noting how he didn't even mention that not only his sister's life was in danger a few hours ago. After all, the boy himself almost got executed for committing treason. "Besides, Tomioka-san and Himejima-san were also there to support you, you know? As well as Urokodaki-sama, even though he wasn't there physically. You sure have made quite an influence here, Tanjirou-kun."
"...You didn't have to go as far as to be ready to commit seppuku."
"That's my choice, not yours," Shinobu flicked his forehead, making him flinch. "It was necessary. After all, most Hashiras are quite stubborn and unforgiving. If I didn't guarantee your allegiance, they wouldn't hesitate to execute you and your sister. Now turn around, so I can examine your back."
Tanjirou did as he was told. Shinobu thought he had quite a fighting spirit, because most Demon Slayers of his rank wouldn't have been able to stay conscious with this many wounds on his body. Did he fight the Lower Moon demon in this state?
"I didn't do it for you," Shinobu said once she was done dressing his injuries. Smiled, when Tanjirou blinked at her in confusion. "I did it for Kanao."
"... For Kanao?"
"Yep. After all, you are precious to her, and she's precious to me," Shinobu patted his head gently, before calling Aoi with a bell. "Kanao will be sad if you're gone. Hmm. Now that I think about it again, she might actually turn traitor if the Hashiras chose to execute you instead."
Tanjirou's eyes widened in surprise. Shinobu chuckled. Oh, he didn't know how dear he was to Kanao, did he?
"You should look for Kanao later," Shinobu waved him goodbye. "She's on an errand now, so she'll be back tonight. She's been looking forward to seeing you again."
Tanjirou nodded and bowed to her, before leaving with Aoi and to the medical ward.
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"Um, is there something in my face?"
Aoi blinked. Leaned back, before coughing into her fist in embarrassment. She didn't realise she had been staring at his face. "I-It's nothing."
Tanjirou hummed. He was silent for a few moments as they made their way to the medical ward. Aoi stole another glance at him. So this was the boy Kanao liked.
"Are you Kanzaki Aoi-san?" he suddenly asked.
"Huh?" Aoi exclaimed in surprise. "How do you know me?"
"Kanao had told me about you a lot in her letters," the boy smiled cheerfully at her. "Blue eyes, straight black hair with a parted fringe and short twin-tails adorned with twin butterflies. Always looks stern but is actually very nice. She had described you perfectly."
Aoi turned beet red. She couldn't believe Kanao had included her in the letters! She was happy that Kanao mentioned about her, but at the same time mortified. Must Kanao describe her in a letter to a boy?
"Y-you look different than what I had expected, though," Aoi said, gesturing to his face. "Kanao has never told me about how you look, so I just assume you look fairly… average." Not naturally striking, with fancy earrings, a prominent scar on the forehead and a rather nice smile. Kanao was one lucky girl, alright.
Speaking of Kanao… "You haven't been sending her letters, have you?"
"Ah…" Tanjirou scratched his cheek. "Mm. Yeah. I've been… busy."
For the whole two and a half years? Aoi wanted to ask. But after seeing the dark look on his face, she decided not to. After all, Kanao herself hadn't sent any letter to him ever since that winter two and a half years ago.
Their conversation was interrupted by a pitiful wail, coming from the room where the other two Demon Slayers were. Tanjirou perked up, relief evident in his face, while Aoi sighed.
"That blonde is at it again…," muttering in annoyance, Aoi pointed at the room's entrance. "Anyway, I'll let Kanao know that you're here once she's back. You can settle down at the second bed from the door while I shut Agatsuma up."
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"You can come out now, Nezuko."
She pushed the door of her box lightly, squinting. The room was sufficiently dark, with the orange sunlight barely penetrating the curtain on the window. She could sense no presence but him alone in the room. Stretching her hand out, she checked if her skin burned. It didn't. It was safe.
She crawled out of the box. Saw him by the window, wincing at the pain when he moved to sit on the bed. She made a beeline towards him, frowning in concern. He smiled at her, reassuring her that it was nothing.
"Thank you for protecting me back on the mountain, Nezuko," he said, patting her head gently. "You had risked your life just so that you could save me. Onii-chan is grateful for you."
She nuzzled his palm. He chuckled fondly. But when she looked up, his eyes were filled with pain and grief. Always like that, ever since that incident. The light that had once brightened his countenance was rarely seen again.
"Tomioka-san, Himejima-san, Urokodaki-san, Kochou-san. So many people have risked their lives just to take care of us," he murmured. "You are precious to me, but I've done barely anything for you. I'm sorry for being so weak, Nezuko. I'm so sorry."
His eyes began to glaze over. The corners of his eyes reddened. No tears fell from his eyes, however. He always tried to look strong in front of her. Never shown any of his weak side.
"I am nineteen now. Already a young adult. And then, I'll be twenty next year. Thirty years old. Fourty, fifty. Without realising it, I will be an old man already. And then I will die, leaving you all alone and suffering," he mumbled, clenching his fist. "I'm sorry for being human, Nezuko. I'm your older brother, but I can't even keep you out of harm's way. It's my fault. I'm sorry. So sorry…"
Her eyes grew heavy, but she couldn't fall asleep now. Not when he was being like this, again. When he wouldn't stop blaming himself for everything. When the guilt tore his heart to pieces, snuffing out his light further, and she could do nothing but watch.
So she held his hand and snuggled into his embrace, letting him know that she was still here. She wished to say something, to soothe his pain and let him know that it was never his fault. But her mouth couldn't form the words. She was too weak of a demon to retain the ability to speak. Too weak, too dependent on him, unable to even comfort him.
Fortunately, her touch was enough to bring him out his reverie. He tightened his hold on hers, caressing her hair gently. Just like how he had always done it back before everything fell apart.
"That's why I have to get stronger. Faster. Smarter. I have to keep fighting," he smiled down at her. There was now a glint of determination in his eyes, to her relief. "I've promised, haven't I? That I will definitely turn you back into a human. Five years, twenty years, forty years. I'll keep on looking, trying, fighting until I can no longer move. And then, you'll be human again. Running happily under the clear sky, basking in the warm sunlight."
Nezuko nodded off, almost falling down onto the floor were it not for the arms that held her. She was running out of energy, but she wanted to accompany him.
"Ssh. You're tired, aren't you? You have been awake for so long, and you were injured this afternoon," he cooed at her, lifting her up so that she could lie down comfortably on the bed. "Sleep tight, Nezuko. Onii-chan will always be here for you."
Darkness soon fell over her, but she never let his hand go.
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Ping.
A distinct sound roused him from his sleep. Tanjirou frowned and blinked, wondering if it was part of the dream. The room was dark, with moonlight barely peeking through the curtains. His neck cricked and his whole body ached as he realised he had been kneeling on the floor by the bed, where his sister laid asleep. Nezuko was still holding his hand.
Something flickered in his periphery.
He snapped awake. There was no one in the doorway. But he thought he caught a scent of flowers and blood. Saw a flutter of a butterfly…
And a glint of a coin.
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Kanao stared at the full moon in the night sky as butterflies floated around her, mind occupied with thoughts of the two people she had just seen in the dark room.
It had been two and a half years since the last time they met. Back when the coal seller house was full of warmth and laughter, they had promised to see each other and dance under the winter moon. It had been two and a half years since Kanao came to see him, only to find the Kamado residence empty but a house dyed red and five fresh graves just outside the carnage.
It felt as if the world had collapsed around her. The faint dark mist that had permeated the house indicated a demon attack. It was not supposed to happen. The talismans should have hidden them from the demons' eyes.
Fortunately, only five new graves were found near the house, four small ones and one adult-sized. There was a possibility that two of the Kamado family managed to survive. That he had survived.
It was a few days after the tragic discovery when Kanao received the news that Kamado Tanjirou and Kamado Nezuko were alive. Shinobu told her that the Water Hashira was the one who had found them, and he had directed them to his master in a nearby village. Kanao felt the clock ticking again.
But the tragedy didn't stop there. Shinobu said that Nezuko had been turned into a demon. And that Tanjirou hadn't given up on her.
It was treason of the highest degree, for a Demon Slayer to care for a demon. But Tomioka Giyuu had let them go, and Urokodaki Sakonji had decided to house them. Kochou Shinobu knew about this but had chosen not to report it. Kanao too; which was why she could not risk sending her crow to check on them.
For the next two years, Kanao received no more news about the surviving Kamado siblings. Only half a year ago did she see his name in the list of participants who had passed the Final Selection. He had become a Demon Slayer, just like her.
And finally, he was here. In the Butterfly Mansion. In her home.
"So you're here, Kanao."
Kanao closed her eyes and sighed. Then, she turned to face him.
He was taller than she remembered. His shoulders were broader and his face sharper, though his long hair had been cut short. He was bandaged all over, a result of the recent battle at Mount Natagumo, while his exposed skin was now littered with faded scars. But other than that, he was the same person she knew. Same scar on the forehead, same hanafuda earrings dangling from his ears. Same red eyes and kind smile.
"Tanjirou-san," Kanao said with a smile. "It has been a while."
"...It's been two and a half years," Tanjirou replied after a few moments of silence. Scratched his head and looked away, when he caught himself staring at her face for too long. "I heard your coin flip just now. Why did you just leave?"
Because I didn't want to disturb you, Kanao thought. After all, she was an outsider. The sight of the two sleeping in the dark room felt strangely… lonely, as if it was an incomplete picture with five missing figures. Tanjirou and Nezuko only had each other now, and Kanao didn't want to intrude just yet. So instead, she said, "Because I've flipped the coin."
Tanjirou blinked, before huffing a laugh. "I guess some things never change."
"I'm sorry if I woke you up," Kanao said. "I wanted to let you rest. I was planning to see you in the morning."
"It's alright," he waved his hand in reassurance. "I've been looking forward to seeing you too. Did you just come back from a mission?"
"It was a minor one," Kanao nodded. Glanced at the bandages around his forehead. "I didn't expect you to become a Demon Slayer."
"...Me neither," Tanjirou chuckled. "I thought I'd be a coal seller till I'm old."
Kanao frowned. He laughed, just like he had always done in the past, but it sounded… off. He may have grown up and became stronger, but she didn't miss the subtle slump in his shoulder. Nor the dimming light that had once brightened his eyes.
"You've changed, Tanjirou-san," Kanao said, fiddling with her coin.
"I have?" He asked, surprised. "How so?"
Her thumb flicked. The coin flew up with a distinct ping, before landing on her palm.
"As if your heart has closed off."
His smile faltered. Silence fell between them.
"... Is that so," he said. Stared at the coin in her hand. "Right. You asked me how to change that time."
"I did," Kanao nodded. "You gave me advice on how to open up my heart."
"I guess, I haven't been following my own words, then," Tanjirou admitted, mouth quirking in another smile. It looked hollow to her eyes. "I've set a bad example. My bad."
Kanao stared at him. His situation was unlike hers, because she did not remember if she was ever as carefree as Tanjirou before that winter. But she had seen another person who was just like him. After all, her own sister had also hid her pain behind a smiling facade, hoping that no one would notice how affected she was by Kanae's passing. Kanao realised that tragedy could also change a person, and often not for the better.
So she did what Kanae had done for her: offered him her coin.
"Maybe you should fall in love with someone, Tanjirou-san," Kanao said seriously. "Then, you'll be able to change for the better."
Tanjirou blinked at her owlishly. Then, he snorted, before bursting out laughing.
Kanao retracted her hand, confused. Perhaps, he didn't really need the coin because this time, his laughter sounded genuine. He only ceased his laughter when he heard an angry yell from inside the mansion to shut up.
"S-sorry," he wheezed, clutching his stomach. "I shouldn't have l-laughed."
Kanao nodded. "You shouldn't. It's night time, and you were being too loud. Aoi will hit you."
"... Um, I'm sorry."
"It's okay," she assured him with a smile. "At least, you finally laughed. Just like the Tanjirou-san I know."
His gaze softened at her words. Then, his hand rose to pat her head.
"Thank you for your advice, Kanao," he smiled softly. "I don't know about me, but I'm glad to know that you've changed for the better."
"... It was Kanae-nee-san's advice. Not mine," Kanao said distractedly. His palm on her head felt bigger than she remembered, but it was as warm as before. "Though, you don't seem to need it now."
"I wouldn't want to take away the coin your sister had given you. Thank you for your offer, anyway."
"Then, have you fallen in love with someone as well?"
"I think I have," he murmured, as his hand slowly moved down to tuck her hair behind her left ear. "Since a long time ago..."
For some reason, her cheeks warmed at his gentle touch. Kanao bit her lip, unable to form words, and looked down to avoid his gaze. She only looked back up when he suddenly stopped caressing her head.
Her heart plummeted. The light in his eyes was gone once more.
"Tanjirou-san?"
He flinched. Shook his head, as if to get rid of an unpleasant thought.
"... Sorry." He retracted his hand and stepped back. Kanao noticed the tremble in his hands. "I… I'm tired. I should go back to my room now."
"O-okay," Kanao said hesitantly. "It's late. You should go back to sleep."
Tanjirou gave her a brief smile. "You too. See you tomorrow, Kanao."
He turned around and left. Kanao had the urge to chase after him, to do something and bring back the spark in his eyes. But he had pulled away from her first, and she wanted to respect his decision.
"See you tomorrow, Tanjirou-san," she mumbled, too softly for him to hear.
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