Fate Changed

Summary: A (timely) return to the Butterfly Estate after a mission, leads to Tanjirou finding out something he shouldn't know. It changes the future.
Notes: What if Tanjirou found out about Shinobu's plan? What if he talked her out of it? Also, something (relatively) quick to tide you over while I work on the second and main part of the Sun Pillar AU. (Someone explain to me why and how I started this behemoth of a project?!) Inspired by fanart I saw on Twitter.

Chapter 1

Tanjirou had just finished a solo mission and was returning to the Butterfly Estate.

This was the second time.

"Feels a little like coming home, right Nezuko?" he smiled.

The box on his back shook.

It was late evening when he reached the home of the Insect Pillar.

Nezuko had come out of her box, since the sun had set.

Tanjirou knocked.

"Hello." he called, "Sorry for dropping in unannounced." he said, as he walked in the garden.

"Hello, Tanjirou-san, Nezuko-san." Aoi greeted them, "Any injuries?"

"A few bruises." Tanjirou sighed, "Mostly tired."

"You can rest here until your next mission. I think Shinobu-sama already told you, you are always welcome."

"She did, but it still feels a little like I am intruding." he rubbed the back of his neck.

Aoi shook her head.

"Go on inside. I have to finish here."

"Maybe I could hel–"

"Go rest, Tanjirou-san." Aoi told him sternly, pushing the Kamado siblings towards the house.

Tanjirou let her.

They walked in and went to Nezuko's room, where Tanjirou set her box down. Nezuko looked like she was going to fall asleep again, so he tucked her in.

"Sleep well, Nezuko." he said softly.

He decided to make himself some tea and sit out on the veranda until he felt sleepy enough, when he smelled blood.

The smell wasn't uncommon, seeing as the Butterfly Estate was essentially the Corps' hospital, but its location was what spurred Tanjirou into action.

The scent came from Shinobu's study.

"Shinobu-san!" he called, as he barged in, sword ready, fearing she had been hurt, only to find the Insect Pillar kneeling by her desk, looking up at him shocked, hand and mouth bloody. Tanjirou was at her side in a blink of an eye, "Shinobu-san!" worry had been replaced by fear.

"Tanjirou-kun? What…?"

"I just arrived. What, Shinobu-san, why are you bleeding? Are you hurt? Should I call Aoi-san?" he fussed, trying to wipe the blood away, to look for a wound, frantic and trembling hands reaching for her.

Shinobu could only stare for a moment longer, before she coughed up more blood.

Tanjirou froze.

"What can I do?" he asked softly. Quietly.

"It'll pass in a moment." she said, heaving a sigh, "I am sorry you had to see this. No one should have."

"What…Shinobu-san, are you ill?"

"No. Not exactly. It's self-inflicted."

Tanjirou looked at her desk, at the cup, the many different medical items he couldn't understand the use of and the heavy scent of wisteria flowers and he paled when an idea formed in his mind.

"Shinobu-san…what are you doing to yourself?" he asked, afraid of the answer, but wanting to hear it, nonetheless.

Shinobu looked up at him and smiled saddly.

"You probably figured it out already. I don't have to say anything, do I?"

Tanjirou kneeled before her, wiping the blood off her lips, then her hand with the sleeve of his haori, movements too tender and too careful, even for him.

Shinobu stared.

"Tanjirou-kun…?" she wondered, her left hand reaching for his face and wiping away his tears.

"Ah, I am sorry." he said quietly, staring at the blood on his sleeve with a frown.

He watched as tears fell on it and he drew that hand away, using the other sleeve to wipe away his tears.

"Tanjirou-kun."

"I can see fellow Slayers shed blood and die during a fight and not have a flashback. But you, Shinobu-san, managed to make me relive the moment I found my family." he whispered, "Why are you doing this?"

Shinobu stood up and gave him a hand.

Tanjirou let her pull him to his feet and lead him to a stool. She sat across from him on another.

"I am sorry. This…I was going to tell Kanao about this. When the time would feel right. You, Tanjirou-kun, who are such a kind and gentle person, I didn't want you to find out most of all. Because then you'd try to change my mind and I don't think I would be able to deny you."

"I…" the young Slayer shook his head, "I don't believe I have the ability to change Shinobu-san's mind, no matter how much I would like to at this moment." he said, still looking at the blood stains on his sleeve, "How can you change the mind of someone so determined to die that they'd poison themselves?"

"It's not because I want to die." Shinobu said.

Tanjirou's head shot up.

"Then, why?"

"The demon that killed my sister was an Upper Moon. Upper Moon Two, to be exact. You've seen how powerful an Upper Moon is. And I can't even cut a normal demon's neck. So, my plan was to be the bait. I had to be devoured and Kanao would cut his neck off. The poison in me would weaken it enough for her to deliver the finishing cut."

"So, your plan is for Kanao to lose another sister?" Tanjirou asked, "For Aoi-san, to lose her teacher? For Naho, Kiyo and Sumi to lose the one protecting them? For the rest of us to lose a dear friend? If you die in battle, you die in battle because your wounds were too severe and your opponent bested you. We cry, we mourn, but we have to move on." Tanjirou said, tears running down his cheeks, "I've seen how strong an Upper Moon is. Akaza is number three. I can't begin to imagine how much stronger number two must be. How could I move on, though, hearing about your death, and knowing that you went in that fight intent to die? How would Kanao, who would be forced to witness it? The idea alone, it's tearing me apart and I've known you only for a small amount of time."

Shinobu reached over and wiped his tears.

"See? I knew you'd say stuff like that." she smiled saddly, "But I don't know what else I can do."

"You asked me to fulfill your sister's dream. Let me take revenge for her in your place. Let me cut the neck of the demon that took your sister from you. Let me carry that, too, for you."

"How much more can one person carry, though? You already carry your sister, trying to find a cure for her. You carry your own anger towards Muzan. I put my sister's dream on you. I can't just give you and my revenge."

"You are not giving it. I am asking to take it. I'd rather be the one looking for that demon, than let you become bait." he shook his head, "Because I have to protect my sister, I can't die just yet. So, I will come back alive from that fight. Broken and bruised, yes, but alive." he said determined, "For Shinobu-san and her sister, I will do it."

Shinobu stood up and walked closer to him. Tanjirou looked at her, his determination shining through his eyes.

She cupped his face and he blushed.

And then she was pressing a kiss to his forehead, a real smile on her lips.

Tanjirou blushed harder, but he couldn't take his eyes off that smile.

"Tanjirou-kun has the ability to change someone's mind. Or, more precisely, someone's heart. It's your kindness. That beautiful soul of yours." Shinobu was saying, "How could anyone listen to your words and not feel moved?"

Tanjirou wrapped his arms around her and pulled her close in an embrace, resting his head against her, just under her chest, something that would normally had made him look like a ripe tomato, but at the moment all he wanted was to hold her close and hide his tears.

"Shinobu-san has suffered too much for too long." he said quietly, "I only wish for Shinobu-san to be alive and happy with everyone here in the Butterfly Estate. I want to be able to come back here and see Shinobu-san again after the battle ends."

He felt a pair of arms wrap around his head, holding him close.

"Shi…nobu-san…?"

"I will fight at your side. Let the three of us kill the demon that killed my sister. With you there, I wouldn't need to sacrifise myself. But I have to be there. I have to see. I need to see."

Tanjirou nodded.

"All right. I'll keep you safe." he promised.

"I'll be in your care." she smiled down at the top of the young Slayer's head, leaning to press a kiss there.

"I'll be in your care, too. Please, take care of me when I get hurt in the fight."

Shinobu chuckled.

"I am your doctor, aren't I?" she smiled.

Tanjirou looked up and smiled back.

"Shinobu-san should start looking for a way to get all that poison out." he said, "And rest more. Shinobu-san smells tired."

Shinobu pinched Tanjirou's nose.

"You really shouldn't say things like these so casually when talking to a woman, you know." she smiled.

Tanjirou blushed.

"I'm sorry. I'm just worried. And I know Shinobu-san won't misunderstand my bluntness."

"Thank you." she said softly, "I'll go rest. You should, too."

"I don't think I'll be able to sleep tonight." he said sheepishly, "A little worried about having a nightmare."

Shinobu looked at her blood still on his sleeve.

"I am sorry. I didn't mean to remind you so vividly of your family's deaths."

"You couldn't know I considered you family." he said, "I don't think I was aware myself." he added.

"Thank you." she smiled softly, "Do you want me to give you a sleeping pill?" she tilted her head to the side.

"Would that mean no nightmates? Then, yes. But first, I want to be sure you will rest." he smiled at her.

Shaking her head, Shinobu gave him a sleeping pill and then let him escort her to the door of her room.

"Give me your haori." she said, "I'll have it washed in the morning. We don't want to worry the girls with my blood on it."

"I can wash it myself, Shinobu-san. You don't have to…"

"It's got my blood on it, let me make up for it."

"Shinobu-san…"

"Please."

Sighing, Tanjirou took his haori off and handed it over to her.

"I'll see you the morning, Tanjirou-kun."

"Goodnight, Shinobu-san." he smiled, "Sweet dreams."

And with that, he left the Insect Pillar at the door of her room, a warm and comforting scent following him.

Early the next morning, on his way to the kitchen for breakfast before training, he finds his haori is already out to dry. He blinks at it.

'Did Shinobu-san wash it during the night? Maybe I should have made sure she actually went to bed before I left.' he thinks to himself, as he prepares breakfast for him and Shinobu-san, 'I will bring her something to eat as a thank you.'

Picking up the tray, he made his way towards her study, as her scent was coming from there.

"Shinobu-san?" he called, "Are you here?"

"Come in." she called back.

"Um…I might need a little help." he said, sheepishly.

The door was opened and Shinobu appeared before him.

"I brought breakfast." he smiled, "As a 'thank you'. For my haori."

"Thank you, Tanjirou-kun." she smiled, letting him enter.

"Um…Shinobu-san?" he asked, as the two sat down to have breakfast.

"Yes?"

"Did you rest last night?" he asked, "I saw my haori and I was worried you…"

"I woke up too early." she replied, "Don't worry." she smiled.

Tanjirou looked embarrassed.

"I am sorry. I understand it might come off as nagging, and it must be annoying, me pestering you to rest."

"Thank you for looking out for me, Tanjirou-kun." she smiled at him.

Tanjirou stared for a second, before nodding once and focusing back on his breakfast.

"Shinobu-san is always looking out for me and my sister when we come here." he said softly, "I just wanted to give some of that care back. It's the least I can do for Shinobu-san."

"Tanjirou-kun?"

"Yes?"

"Do you still wish to help me kill that demon?"

"Of course! I'd kill it for you, if you want me to." he replied seriously.

Shinobu nodded once.

"Then, when the time comes, when I find where it is, I will send you a crow. We'll have to move quickly. And I'm counting on you and Kanao to cut its neck."

Tanjirou thought about it for a moment.

"Shinobu-san will cut its neck." he said, finally.

Shinobu blinked.

"Tanjirou-kun, you know I can't do that."

"Maybe not when you hold your sword on your own." he smiled, "I will lend you my strength, my arms and my sword to do so. It's your revenge. I am a willing accomplice, aiding you. I'll be your second sword."

Shinobu stared at the young Slayer across from her, before a soft smile appeared on her lips.

"Then, please lend me your strength."

"Of course!" Tanjirou smiled.