Kimetsu no Yaiba/Demon Slayer Isekai. Female lead.

Oyakata-sama's

"CAW CAW! Namikaze Haku! Namikaze Haku!" Haku was awoken to a crow at her window. Was that crow.... Talking to her. She jumped up and opened the window. "You must be my kasagai crow from Kagaya-san!" The crow landed on the windowsill and presented a letter to Haku. She reached out and accepted the letter, patting the crow on the head. "Thanks buddy. So what's your name anyway?" The crow looked at her slightly confused. He must not have a name yet. She looked the crow over, noting one of its wings was actually white. "How about Wuxing?" The crow flapped its wings and cawed in approval. "Good!" Haku chirped her own approval, then reached into her pocket for a piece of honey candy which she gave the crow. "Thanks for your hard work Wuxing." Wuxing flew off and Haku knew she could call on him if needed. She sat down at her small desk and opened the letter. It was from Kagaya.

' Dear Haku,

I hope your training is going well. Your demon slayer uniform is being prepared for you as well as your katana. It is usually tradition for each slayer to choose their ore after selection, but given the circumstances around your enlistment, I took the liberty of choosing for you and I apologize. Your smith should be by the Rengoku residence in around 10 days. His name is Haganezuka Hotaru.'

Wait , the same Haganezuka as Tanjiro? The one who is surprisingly hot and whose dedication to his craft is beyond admirable? She squealed internally and continued reading her letter.

'I would like to invite you to my estate to discuss what knowledge you have in regards to Kibutsuji Muzan. I will have Sanemi escort you here as Rengoku will be busy. He should arrive within the day. I look forward to our meeting.

Ubuyashiki Kagaya.'

Kagaya was so kind. She was also excited to be receiving her sword. What color would it be? Haganezuka always wanted to see a red one, so maybe it would be red. Green would be cool too! She folded the letter feeling a slight sting on her finger. "Ouch! Paper cut!" She exclaimed and instinctively brought her finger to her mouth. She froze, slowly removing her finger from her mouth. There was no metallic tang of blood as one would expect. It tasted sweet and floral like the nectar of a honey suckle. When she looked at the finger, she was even more astonished. The blood that seeped from the tiny wound was blue. What did this mean? Sure this was a new world, but blood was blood right? Every human bleeds red, right? Would the demon slayers think she was some kind of demon? "Haku-san! Haku-san!" Her door slammed open and she jumped, turning swiftly and holding the injured hand behind her back like a child hiding a cookie. Rengoku stood in the doorway. "Ah so you are awake. I knocked several times and you didn't answer. Are you alright?' He took note of her strange behavior. "I'm fine Kyojuro-san. Just engrossed in my letter from Kagaya-san." He relaxed a bit, seemingly satisfied with her answer. "Yes. Sanemi is supposed to be here later to escort you to Oyakata-sama's estate. Come, let's have breakfast." Haku nodded and rose to follow the hashira. Her finger had already stopped bleeding and she debated on telling him about it. She decided against it. Kagaya may be fine to tell, he could even get her in touch with Tamayo who may be able to get her answers. But what if he kept her from being a demon slayer because of it? She decided she would keep it to herself for now.

It was afternoon when Sanemi arrived. Haku was a little nervous given his temper and how he had demanded she tell him what she knew before. She hoped that Kagaya having taken her request for privacy would deter him. "Hello Sanemi-san." She greeted the wind hashira with a slight bow. "Whatever lets go." He motioned for her to follow and they headed towards the mansion, in the convoluted way one did to avoid its secret location being revealed. Sanemi was mostly silent the whole time, giving only grunts and glares if Haku asked a question, though she did notice him occasionally staring at her to which he would quickly avert his gaze. When they arrived at the Ubayashiki manor, Sanemi headed into a reception room. "When you're finished with Oyakata-sama, I will take you back to the Rengoku estate." Haku nodded. "Thanks, Sanemi-san." She smiled at him and he seemed slightly unnerved by it, stiffening and looking away. Soon, the oldest Ubuyashiki daughter Hinaki came to escort her to her father. Honestly , the quintuplets were difficult to tell apart aside from Kiriya since he had black hair, and despite often disguising as a girl, was a boy. She was escorted into a room where she sat across from Kagaya. Amane was also there and poured tea, to which Haku gratefully accepted.

" Now then Haku-san. I hate to rush, but we are all curious what knowledge you have in regards to Kibutsuji Muzan." Kagaya smiled softly, his sightless eyes still focused on the girl before him. Haku kept her tea cup at her lips a moment before sitting it down. "I know about all of the upper moons, their names, ranks, and abilities. I also know about Muzan's desire for the blue spider lily." Amane gasped and Kagaya's eyes widened. "You know this is quite difficult to believe without some suspicion you could be involved with Kibutsuji himself. May I ask HOW you have this knowledge?" Haku fidgeted in her seat. No, maybe if anyone would believe her it would be Kagaya. "I'm not from this world, and I don't just mean I'm from America. I mean from a different world entirely, and in that world the story of Muzan as well as his demons and how everything ends for the slayers in this generation is in a book. In fact, it even goes as far as telling the location of the blue spider lily." Kagay was silent for a long time, taking in everything the white haired girl had said. He detected no lies. "So the blue spider lily is real as well. You must not allow Kibutsuji to find out." His words were soft and kind, but contained a hidden threat deep within; Kagaya would do anything to stop Muzan and protect humanity. "The flower is so rare it hardly even appears in the location it grows anyway. I would never tell Muzan anyway. He is nothing but a cowardly being, cruel and selfish to the core. The world knew he would be such a plague he was even born dead. I know it may not be my place to change the future, but I want those who suffered in this world to have a chance at happiness." Haku's conviction was real and Kagaya could feel it. It was also interesting to hear that Kinutsuji was stillborn. " Now then, what of his upper moons?" Haku began to explain the names and abilities of each of the moons. She left out backstories as she felt it would provide little to the demonslayer corps overall. Kagaya was silent again after she finished. "Haku-san" he finally said, "I choose to believe what you say is true. I would still like you to join the demon slayers under the conditions discussed before. I will not ask questions about the outcomes you are aware of. Best not to know the future after all." Kagaya paused again and Haku was beaming. "Do allow me this one foresight." Kagaya said with a tinge of fear in his voice. "Is... is Kibutsuji Muzan destroyed?" Haku smiled softly, "He will be finished in this generation." Kagaya seemed relieved and elated. "Thank you Haku-san. Please, join Sanemi and travel safely back to the Rengoku estate." As Haku left she was sure Kagaya was crying.