Headcanons of platonic kanao with a child reader that looks up to her as a big sister? Maybe reader was saved by her and they no longer have a family so kanao took them in to work at the butterfly mansion.
Kanao had been on a mission of her own, hunting a Demon that had been seen around the area she was in. She was precise as she followed her leads and finally caught the Demon red-handed.
Literally, it had just killed someone, a poor soul she was too late to save, but she took on the Demon and beheaded it, successfully killing the monster.
As she was praying for the victim, she heard rustling from the bushes nearby.
Did the Demon have an accomplice? Kanao was on her guard as he drew her sword and approached the shaking bush...! But then she heard weeping, and her eyes widened as she saw a small child, hugging themself while crying.
"Oh my..." Kanao immediately lowered her sword and put it away as she looked at you.
"There there, little one..." She said gently as she carefully reached for you, noting that you were rather skittish.
"I- Is the monster dead...?" You asked, and the young woman gave you a small nod, "It's dead now."
"M- My auntie-?"
"I'm sorry..." Kanao frowned slightly, "She didn't make it..."
"I'm scared..." You said, and Kanao pressed her lips together as she tried to figure out what to do with you.
"Where is your family?"
"They're in Heaven..."
Oh no, that made things much more complicated. She couldn't just leave you on your own in the middle of the road in the woods.
Her hand immediately went to pick up her coin, ready to use it to tell her what she should do with you... But then she remembered Tanjiro and her hand stillled.
"Would you..." She struggled to find the right words, "Would you like to come with me?"
"W- Where?" You asked, your voice so small. Kanao hummed, "Somewhere you are safe?"
After a small silence, you nodded and got to your feet, your hand immediately grabbing the hem of Kanao's skirt, like it was your lifeline in a stormy sea.
"Here," She offered her hand to you, "Take my hand."
You sniffled slightly as you took her offer, wrapping your smaller hand around her petite fingers the best you could, and the two of you left the forest...
It took you a day or two to make it to Butterfly Mansion, where Kanao's older sister, Shinobu, mainly worked, and the elder sister happily invited you to live with the Butterfly girls.
Kanao was glad to see that you had a place where you could rest in peace, a new place to call home.
What she didn't expect was for you to grow so fond of her.
It started off with some little things. Whenever she was around, you would follow her around like a small lovesick puppy, but as soon as she looked at you, you would flinch and hide around the corner, and once she averted her gaze, you would tail her again.
It was cute, or so Shiobu, Aoi, and the three girls, Sumi, Naho, and Kiyo, said, but Kanao herself didn't quite understand it.
As time passed, you grew bolder, not hiding yourself anymore when she would look at you. No, you smiled and stayed right there behind her.
"Can I help you somehow?" She asked once, and you shook your head, "No, I just love my big sis Kanao!"
"Bis sis?" Kanao was honestly confused, wondering why you called her that, but before she could ask, you opened your arms and hugged her, "I love big sis Kanao! I want to always be with you!"
"I..." The young woman didn't understand how to react, "I appreciate it... But I need to go away again eventually?"
"It's okay!" You smiled as you squeezed her one last time before pulling back and smiling at her, "I'll wait for you here! I'll help and do my best so you can be proud of me!"
"I see..." Kanao nodded, giving you a small, kind smile, and gently patted the top of your head, "I trust you to be a big help around here while I'm gone."
"I'll do my best for you, big sis Kanao!" You nodded proudly, and the young woman nodded... And smiled at you.
Was this how her sisters Kanae and Shinobu felt when they took her in? She couldn't help but be proud of you. You were young and already doing so much to prove yourself and your worth. And you looked up at Kanao so adoringly.
She swore she would make it back to Butterfly Mansion no matter what. She didn't want to let you down, not now or ever.