Kimetsu no Yaiba/Demon Slayer Isekai. Female lead.

The Demon King

Haku had not intended to fall asleep, but she was still fatigued from her run in with Douma, training, and being slammed by Akaza. When she woke, the sun no longer came through the crack in the wall. It was night time. She looked around and did not see Akaza. Was this her chance? Quickly she headed out the door of the hut only to run straight into Akaza who wrapped his arms lightly around her. "You're not going anywhere." He said flatly. Haku just sighed and hit her forehead against his chest. Not that lucky. Akaza then scooped her up in his arms. He headed towards a booking sound Haku almost immediately could identify. When they broke through the brush and into an open area above a village, Haku could see them. Fireworks. Her eyes widened with excitement and she smiled big. "Akaza! Look! It's so pretty." when she gleaned back at the demon he had a small smile on his face. "I heard them and went to check it out. I find I'm drawn to them for some reason." Haku already knew why. He and Koyuki got engaged during a fireworks show. Akaza sat down and placed Haku in his lap. Whether it was to assure she did not run off or not, Haku did not care. She stared up at the sky as it exploded with colors. Something about ancient fireworks was far more captivating then the modern ones she had seen before back in her world. In fact she had not thought much about her life before getting isekaied. She had become so invested in the outcome of this one. Was her father ok? Did her grandparents worry when she did not make it? She leaned back against Akaza's chest, and felt the demon stiffen up a little then relax. "What is it?" he asked. Haku looked solemn. "Just thinking about my family and home." "Were you not always here in Japan?" Akaza asked. Haku shook her head. "No. I'm from a land called America. Not to mention I'm not even from this w-" She stopped herself. She should not reveal too much. She was sure Kagaya still only half believed her. Akaza looked at her quizzically, but did not push the matter. Muzan would get it out of her. Oh yeah. He was supposed to take her to Muzan. Akaza had come to dislike that idea, but there was not much he could do against the demon lord. One word and Akaza would be dead.

When the fireworks ended Akza stood up, still carrying Haku. he made his way to where Nakahime was to open the door to the infinity castle. Haku's eyes widened as the door opened and Akaza took her inside. This was bad, really bad. Haku buried her face into Akaza's neck as he dropped down into the infinity castle. The demon in turn, nuzzled her long white hair. She smelled so nice. He continued to hop from moving part to moving part as he made his way to his master. His stomach churned. He did not want to do this, but unless he could be freed from Muzan's control like the Kamado girl or Tamayo he was doomed. He landed on the final plattform with a jarring thud. "Akaza, excellent work." Halku's blood turned to ice. That voice belonged to the one person she had hoped to avoid, Kibutsuji Muzan. Still in Akaza's arms, she took a few short breaths and bit her lip as she turned her head toward him. She needed to be strong and show little fear. Her red eyes locked with Muzan's. The demon sood before her in the form of a child, looking at her down his nose. "Now woman, tell me how you could possibly know things beyond your comprehension." Haku took a deep breath. "Never." Instantly her arm stung. Akaza had moved to hold her tighter, lessening the blow. Blue blood seeped from a wound on her shoulder. Muzan's eyes instantly widened and he moved to stand directly in front of them, returning to his usual form of a handsome man. "Why is your blood the same scent and color as that damned spider lily?" Haku shook her head. "I couldn't tell you that one even if I wanted to." It was true. Shen had an idea of its uses, but overall had no clue why. Muzan placed a finger on her wound and licked the blood from it. He instantly threw his head back, reveling in the wonderful taste and the slight power it seemed to give him. He snapped his head back down and snatched Haku from Akaza, holding her by the neck. Haku grabbed his arm to steady herself. "You will be obedient or it will be quite unpleasant for you." Muzan warned her. Haku kept struggling to free from his grasp. "You're nothing but a coward who sends others to do his dirty work. Go burn in the sun!" He sunk his claws into her skin, bringing blood. "You dare speak to me in such a manner? I could end your pathetic life right now." Haku spat at it "Then you wouldn't get your answers. Not that you'll get them anyway." Muzan slammed her into the ground, driving every ounce of breath from her body. "I can make sure your stay is miserable. I'll bring the heads of all the demon slayers to you and make you look at each one in the dead cold eyes." Haku struggled to speak. "M- may-maybe t-they bring me yours instead." That hit a nerve. Muzan threw her across the infinity castle where she slammed into a wall, crashing through into an empty room. She slumped down to the ground. Haku's already weakened body could take no more and she reluctantly fell into the black abyss.