Kimetsu no Yaiba/Demon Slayer Isekai. Female lead.

First training, First Flutter.

Haku awoke to a soft knock at the door. It was Senjuro. "Haku-san, breakfast is almost ready. You can clean up in the facilities across the hall." While he spoke, Haku rose with a long stretch and walked to the sliding door, opening it as he finished. "Thanks Senjuro-san. I'll be right out!" Senjuro bowed slightly and headed back towards the kitchen and Haku made her way into the restroom across the hall. She splashed water on her face and looked in the mirror above the wash bin. There was something on her neck on the right side. She moved her long white hair to her left shoulder and touched the strange mark. It was shaped like a heart and felt no different than the rest of her skin. Was this a demon slayer's mark? She had no such mark before coming here, just that weird little mole on her left butt cheek. 'So I've only got 5 years left to live?!?! No, no, not necessarily. I mean, Tanjiro and Sanemi survived in the original ending.' She bit her lower lip and sighed. That was the last thing she needed to worry about right now. She slapped both hands against her cheeks and headed to the dining area. Senjiro was just sitting down and Rengoku sat, arms crossed on the other side. "Ah, Haku-san. Good morning. Come sit beside me." he patted the cushion to his right. Haku smiled and sat down next to him. "Good morning guys! Food looks amazing! I've actually only had a traditional breakfast a few times before!" Senjuro smiled, "Well I hope it's to your liking. I've already taken father his share so dig in." Rengoku picked up his chopsticks and dug in. "Tasty!" He boomed. Haku picked hers up and joined in. She hated the look on Sanjuro's face at the mention of his father. If she were able to snap him out of his drunken depression, perhaps he could help in the battle against Muzan. He was a former hashira after all. She pushed that from her mind for now and just enjoyed the food.

After breakfast Rengoku turned to you. "Now then Haku-san do you have any experience with the martial arts or swordplay? I'd like an idea of where to start in your training." Haku nodded. "I actually do a mixed martial arts class. It's been a while, but my father made me take kendo classes. He was somewhat of a prodigy in his younger years, so I heard anyway." "Good to hear. We can begin immediately if you'd like."

To say training with Rengoku was tough would be an understatement. They had been drilling for hours, and she was beat. Her hands had blisters from gripping the wooden sword so tight and parrying Rengoku's attacks. He was going way easy on her for sure, but his hits still packed a punch. She stumbled back after blocking another strike only for Rengoku to follow up with another right after. He slashed from up high and was bringing the wooden sword down towards her head. He stopped right before hitting her full force and simply bonked her on the head, throwing her the rest of the way off balance. She fell onto her backside with a thud. "Ouch! Kyojuro-san! You're too fast!" He bellowed out a heart laugh. "That was nothing. Demons are much faster. Besides, you are incredibly quick to react to most of my strikes. Just like with that demon before. You have great potential." He stuck out his hand to help Haku up who accepted it gratefully. "It makes me happy to hear that. I want to become as strong as I can Kyojuro-san!" She smiled big, making Rengoku blush slightly. He had found Haku to be quite beautiful from the moment he laid eyes on her, crouched beside the injured Kamado, and seeing her determination made her even more so. He noticed her wince slightly when taking his hand. He rolled her hand over in his to see the blisters that had formed. "Come. We will get this treated right away." Before she could reply, he led her inside and had her sit down while he grabbed the first aid kit. He then returned to her side and grabbed her hands. "Kyojuro-san, I can do it myself." He chuckled. "Nonsense. You are currently in my care so I will help with your wounds." Haku gave a small smile secretly happy to have the handsome hashira fuss over her. He applied ointment and wrapped her hands. When he was finished with the second hand he held onto it for a while, rubbing his thumb over the palm. Haku simply stared at him, her cheeks tinted pink. "K-Kyojuro-san." His flame colored eyes widened a little when he realized what he was doing. He gently released her hand, his own cheeks tinted pink as well. "Ah, yes! That should do it." He stood up, securing his sword to his side. "Please, go to your room and rest. Practice your breathing some as well. I have some business to attend to and then patrol later." Usual smile on his face he turned and left. Haku held the hand he had caressed close for a moment. She then got up and headed into her room, laying on the futon. Her heart was beating fast. Before long she fell to sleep.