Kimetsu no Yaiba/Demon Slayer Isekai. Female lead.

Defeating an Upper rank Demon

Haku ran outside catching a glimpse of the trio fighting Daki. She breathed deep and screamed so all could hear. "We have to cut both their heads off to win!" Everyone acknowledged her including Gyutaro and Daki. Uzui came flying past, slamming into the building. Haku lunged at Gyutaro "Inyo breathing, seventh form, Onmyoji's Shikigami!" A second Haku appeared attacking Gyutaro from the front while Haku came from behind Gyutaro. Gyutaro slashed the Haku in front of him and it crumbled into a piece of paper. Haku went for the neck, but Gyutaro brought his arm up to block. It was chopped off instead. The demon hissed. "Little wench. And it's taking forever to heal." He brought his other sickle around. Haku twisted to dodge, throwing her hand up to block her, and the sickle scraped her palm. Fresh blue blood seeped from the wound. Gyutaro chuckled, now recovered. "Wow. poisoned already. Your blood smells amazing! It being blue is quite strange though." His arm Uzui appeared, having recovered. "Who's weird now?" On the roof above Hinatsuru fired wisteria laced kunai. Gyutaro did not completely dodge, and Uzui rushed in, some of the kunai hitting him. Uzui sliced off his legs, which did not heal quickly. Gyutaro summoned more blood sickles and rotated his arms. "Rotating circular slash!" Uzui had to back off. He landed beside Haku. "How are you? The poison?" He was highly concerned. Haku, surprisingly, felt fine. She was totally unaffected by the poison. "Im.... fine." Uzui nodded and lunged at Gyutaro again. Haku joined, slashing at the sickle wielding demon. Haku looked up to see Inosuke running around with Daki's head. Good. One down. A vicious dome of blood sickles came at Uzui and Haku. The two tried their best to block them all, but were thrown back violently. Haku landed on top of Uzui who was quite beaten up. He had a cut on his abdomen that was purple with poison. This was bad. Haku heard Tanjiro scream that Inosuke had been hit. Daki's head was returned to her body. Haku was still laying on Uzui's chest. He lifted her up. "The hell is up with your blood. It's blue! And smells sweet! And the poison ain't done nothin to ya!" Haku flailed about a little. "I have no clue! But Inosuke, Tanjiro, and Zenitsu are in trouble!" Haku noted how Uzui was panting. Wait.....her...blood....HER BLOOD. She slammed bleeding palm to Uzui's mouth. "I know it's weird but drink this!" Uzui struggled underneath her. Maybe this would help his strength at least. Tamayo said it enhanced blood cells. Uzui relented and drank some. "The hell! It's sweet! Did you eat too much candy or something!" Haku got off of Uzui. "I didn't eat candy! And that's not how diabetes works!"

Uzui had a big grin on his face. "Well whatever it is, I feel great!" The sound hashira rushed back to battle. Haku went to join when a sash wrapped around her waist, throwing her into the nearby roof. Daki laughed. "Just give up and let me take you to Lord Muzan." Haku gathered herself and ran at Daki. "Inyo breathing, fifth form, Gogyo, five slashes!" She repeated the technique multiple times to defend against the incoming assault of sashes. Finally, she was right at Dakis' neck. "Inyo breathing, third form, Unification of Kon and Haku!" She beheaded Daki. Grabbing the head, she ran, only to end up slamming into Gyutaro. He reached down, lifting her chin. "Cutting my sister's head off was a bad idea. I may not be allowed to kill you, but I can sure make it hurt." Uzui was on him in a heartbeat. His skills sharper than ever, his speed doubled. Inosuke came in from behind, poison healed by Nezuko's flames. Gyutaro was cornered. "GO!" Haku screamed. Tanjiro came in as well, using Hinokami Kagura he managed to behead Gyutaro. Haku dropped Daki's head which was screaming and crying in protest. Gyutaro's body burst out blades in mass. Nezuko used her flames to destroy most of the blades, but the entertainment district was left in ash.

Everyone, including huddled together crying because they had won. Haku's blood had cured Uzui's poison, and Inosuke had moved his vital organs upon impact, so he would be fine. Zenitsu woke up crying, having damaged his legs when he first beheaded Daki. Haku's body was sore, various cuts littered her body. She sighed heavily. It was over, and Uzui did not lose his hand this time. Tanjiro went to gather blood and find the siblings' heads. While he was away, Obanai had appeared, sent by Kagaya, but arriving too late. He was disappointed to hear Uzui would be retiring. Haku knew he would come for the final battle, so it would be fine in the end. He and his wives left before the Kakushi arrived. Obanai left as well.