Kimetsu no Yaiba/Demon Slayer Isekai. Female lead.

Pissing Demons Off

Haku slowly opened her eyes. She was laying in a European style bed. She looked around the room that was dimly lit by candles. Haku tried to move, but her body was too fatigued. The room seemed largely empty aside from the bed and a small table on the other end of the room. The door to the room slid open and a pair of cold eyes met hers. Muzan stepped into the room. "I suppose I'm surprised it only took you 3 days to wake up." It had been 3 days? Haku sighed, not entirely surprised given she had used Rokkon Shojo. Muzan walked to the side of the bed and took her arm where he inserted a needle and took some blood. "You're only alive because I have yet to find a way to have only the immunity to sunlight when consuming your blood. Too much destroys the demon cells like the sun. Apparently it managed to sever my link to Akaza. Quite annoying indeed." Haku followed him with her eyes as he walked to the other side of the room. "I am growing tired of the hashira getting in my way and I have no need of the blue spider lily now, so there is no need to create more of my own kind. I believe you are the perfect bait to lead them all to their doom." Haku forced herself to sit up and glared at Muzan. "No matter what, I won't allow it. In the name of Yoriichi Tsugikuni and all the slayers who've died!" Muza's eyes widened at Yoriichi's name. He moved across the room and grabbed her by the throat. "How do you know that name? You're not a descendant of him." Haku smirked. "No, but I'm certain I am only here because of him." Muzan narrowed his eyes. "What do you mean by that?" Haku pondered on it. Would telling him now change anything? "I know everything about you. How you were born dead. How you killed that doctor before being fully cured. How you fear death and change. How Yoriichi almost killed you. He's why you lost Tamayo." Muzan's eyes were wide and he dug his nails into Haku's skin. "How could you possibly know all of this!?" Haku rather enjoyed seeing the demon squirm. She glared at him, refusing to answer. He eventually released her and stepped back, anger clear on his face. "You will answer me eventually. When I bring the heads of the hashira and those little friends of yours." He turned and left the room.

After some time had passed, Haku made her way to the door of the room. She opened it and it led into another room where the newest member of the upper moons Kaigaku was leaning against the wall. Haku knew what a narcissistic coward he was. He cut his eyes towards her as she walked into the room. "Well well well. Someone decided to try and make a run for it." He moved to stand in front of Haku, cupping her chin and leaning her head back to look up at him. "Not bad looking and you smell quite nice." He placed his other hand on the small of her back and pulled her into himself. "Why not have some fun instead. It'd be a shame to cut up that pretty little face of yours." Haku remained as calm as she could, though inside she was shaking with anger. "I'd rather die. You betrayed Gyomei and those children in the temple, and you betrayed your master." Kaigaku tightened his hold on her. "I've never told anyone about the temple. As for my master who cares. He was just a foolish old nobody who wasted his time trying to train a worthless cry baby when I was right there." Haku wrapped her arms around Kaigaku who smirked thinking she was giving into him. "Zenitsu is a million times better than you. Inyo breathing eighth form: Tori to uke!" She slammed Kaigaku into the ground, snapping his neck and various other bones. She then jumped back away to the other side of the room. She leaned against the wall to steady herself. She was still weak from her previous battle. Her sword was with her miraculously enough, but it would be little more than a butter knife in her hands at this point. Kaigaku gathered himself up, a livid expression on his face. "You little wench. I'll eat you while you're still breathing!" He lunged at Haku who managed to roll out of the way. She rushed through one of the doors and down a set of stairs. She jumped off the stairs down onto another platform. Kaigaku was hot on her heels. Why'd she have to go and piss him off. She dove out of the way of an oncoming attack. Kaigaku ended up punching a hole through the wall behind her and haku tumbled down a set of stairs that led to nowhere. When she reached the last stair, she swung herself up under it and into another room. She stood up to run again and face planted into a hard chest. A pair of arms grasped her shoulders and a voice went to ask a question before Kaigaku came crashing into the room. He pointed his sword at Haku. "Kokushibo let me have her." Haku looked up to see six eyes looking calmly at Kaigaku. "You will cease this at once. We are prohibited from killing her." Kaigaku groweled. "She attacked me." Kokushibo looked down at Haku, whose breath was heavy, her legs shaking from using what little strength she had. "You likely deserved it. Now leave." Kaigaku looked like he wanted to protest, but she turned and left the room. He stood zero chance against Kokushibo. Haku let out a sigh of relief. Kokushibo lifted her chin to look at him. "I don't know what all of that was about, but you will behave yourself. Don't think just because we can't kill you that you're untouchable." He released her and guided her to sit at the table in the room. "I suppose I'll take charge of you for the time being." Kokushibo vanished and reappeared a few moments later with a plate of onigiri and tea. He placed the onigiri in front of Haku and sat down beside her. She nervously folded her hands. "Thanks for the food." She picked up one of the onigiri and started eating it. Kokushibo proceeded to sip his tea.

Haku finished her meal and glanced at Kokushibo. "Your demeanor really is a lot like Yoriichi's." She had not meant to make the comment aloud. Kokushibo turned his attention to her. "How could you possibly know anything of my brother?" Haku closed her eyes. "It may seem strange but I have met him before. And I know about your past, too." Kokushibo eyed Haku, trying to decide if she was serious or delusional. Haku decided to continue. "Being an older brother outshone by the younger must have been rough. Choosing to be a demon though, is just sad. Envy is an ugly color on anyone." There was a fleeting look of agitation on the demon's face. "Becoming a demon was another way of becoming stronger and living. Abandoning that would be exceedingly weak." Haku smiled softly and looked at Kokushibo. "Take a look at that flute in your pocket and tell me death is why you became a demon." Kokushibo could not hide his shock. Haku went to stand, but found her legs had left her. She sighed and mumbled to herself. "I had wanted to leave after that one, in case I pissed you off." Kokushibo was slightly agitated, but more confused than anything. He thought about his brother and remembered when he struck down his aged body. Had that really been what he wanted? He looked at the girl beside him. She was nothing like his brother yet he could not help but sense his aura within her. He felt a light pressure in his lap and looking down found that the girl had fallen to sleep sitting up and tipped over into his lap. He reached down and moved her hair out of her face. He would leave her be for now.