Kimetsu no Yaiba/Demon Slayer Isekai. Female lead.

Upper Moon 2: Douma

It was very soft. That was Haku's first thought when she woke up. She heard a crowd of people mumbling as they shuffled out of the room. She laid upon a stack of plush pillows with her head in the lap of none other than Upper Moon 2 Douma. She sat up quickly and Douma chuckled. "Well you weren't out nearly as long as I'd hoped. It's still not nightfall." Haku shivered, still cold from being frozen, as well as with discontent. Douma lifted her up, sitting her in his lab and wrapping his arms around her. "Now then that's better right." Haku felt sick. He was hot, but he was a psychopath. Like a real one. She felt teeth nibble her neck and became rigid. "You smell too good not to taste." He sunk his fangs in, holding Haku imobile as she tried to squirm. She felt Douma stiffen. He pulled back from her neck, blue blood on his lips. "AMAZING! I feel invigorated!" He tilted Haku's head back to look up at him. "My dear you're lucky Lord Muzan wants you. An arm or leg would be fine perhaps? You can live without that. No, I mustn't." Haku held the wound on her neck and glared at him. Douma came down from his high. "If looks could kill." He commented as he caressed her cheek. He pushed Haku down, hovering over her. "I want to taste all of you." This was bad. Really bad. She felt her shirt tear, revealing her breast and bra underneath. Douma cupped one of her breasts in his hand. "Quite beautiful indeed." Haku wanted to scream, but even if someone came, they would only end up dead. She wrapped her legs around Douma who seemed pleased, thinking she was giving in to his pursuit. "Inyo breathing, with form, Tori to Uke!" She used the max amount of power she could manage to flip him, snapping neck, spine, arms, and legs as she did. She moved way faster in this state and managed to grab her sword. She turned just in time to block an attack from Douma.

Haku jumped back from the demon. She just needed to get outside. "Inyo breathing, tenth form, Rokkon Shojo!" She heightened senses to the max. Douma's body became clear. She could see his muscles, bones, then organs. Every bit became visible to her. She lunged forwards "Inyo breathing fifth form, gogyo, five slashes!" She aimed for vitals, and muscles which when cut rendered one imobile. "Inyo breathing, seventh form, onmyoji's shikigami!" Another her melded off from her body as paper and formed a human shape. It continues to attack Douma while the real Haku bolted for the door. She burst through and dashed for the exit. She felt him close, but he had to retreat as she burst out of the temple and into the sunshine. Everything hurt and she was on fire.

She had used some of her most draining moves in quick succession. She limped along, using her sword as a cane. Her shirt torn to shreds she only had her haori to try and cover herself with. After a long while walking she could make out a village just ahead and she tried to speed up to head towards it. She felt arms wrap around her, she flailed about trying to get out of their grasp. "LET GO! I'M NOT GOING TO MUZAN EVER!" The arms lifted her bridal style and she was able to see their owner, Rengoku Kyojuro. He had a worried look on his face, the same as his little brother often carried. "Haku, it's just me Kyojuro. I'm so sorry. What happened?" Haku stopped fighting and wrapped her arms around Rengoku's neck crying. "Upper moon 2. Douma. I encountered him. I couldn't kill him. He.... he tried to..... And I used Rokkon Shojo....and...and..." She was trailing off, unable to keep speaking normally. She went limp in Rengoku's arms. Rengoku held her close to his chest. "I'm sorry I couldn't protect you." he murmured into her ear.