"What do you want?" Shinobu asked as she suppressed her inner turmoil, She glared at him because he made her jump like a frightened kid.

"At the rate you are going, you'll damage your body rather than improve it," Yuu said flatly, he has been keeping an eye on the way Shinobu trains from the roof, she was very extreme to the point that Yuu thought it was reckless.

"What?" Shinobu's eyes were filled with anger as she looked at Yuu.

'You know what I said,' Yuu wasn't bothered by the glare as Shinobu could understand what he wanted to say with his expression even when he wasn't saying anything.

"Don't butt into my training, This is the only way for me," Shinobu said as the difference between her and Yuu was very apparent.

"Are you saying this because of my physique?" Yuu asked as he understood her point.

"If you understand then go away," Shinobu turned around looking away from Yuu.

"I wasn't that different from you before," Yuu said making Shinobu look around.

"Are you making fun of me?" Shinobu's eyes flickered with anger, there was no way she would believe that. A guy like Yuu used to have a small physique like her before? That is the most ridiculous thing she had heard in her entire life.

"Why would I do that?" Yuu tilted his head as Shinobu's face twitched, this somehow was more insulting than before.

"I am not lying, I also had a small physique similar to yours till I was 9 years old, after that I trained and then became like this," Yuu said flatly, he wasn't joking or lying, before he came into this world, Tachibana Yuu was a scrawny kid. 

He even looked younger than his peers because his body was underdeveloped. Afterward, Yuu trained using the methods from his previous life to increase his physique but that too was limited, partly because of his family as he couldn't get too extreme.

'It could've been better if I started before but no point thinking about it,' In his previous life Yuu had started this type of training when he was 4, or more like he was ordered to do it.

"Stop messing ...with me," Shinobu gripped her hands tightly glaring at Yuu.

"I am not messing with you, I have no reason to do that nor do I have any desire to. I am simply helping you because you want to protect your family, I respect that drive of yours," Yuu said standing in front of Shinobu making her look up.

"Damn it, If I find out you are deceiving me, I'll kill you," Shinobu gritted her teeth looking at Yuu.

"You are free to try," Yuu said flatly making Shinobu clench her fists, She knew very well that it isn't going to end well for her if she chose to try it.

"Sit down, and I'll tell you about the method, With this, you'll be able to behead a demon with your won strength," Yuu said as Shinobu's eyes widened, this was her biggest roadblock, her physical strength. 

She didn't have enough strength to cut off a demon's head which made her look for alternatives to kill demons because she couldn't stop herself from being a demon slayer. And now she had even more reason to not give up.

'Is there really such a method?' Shinobu's hand clenched tightly as she looked at Yuu, all she could see was his flat look which she couldn't read at all.

'If he is lying, I'll really kill him no matter the means,' Shinobu thought as she listened to Yuu's explanation with full attention.

"I see, so it works like this," Shinobu nodded as Yuu also told her about the reason the method works in great detail, Shinobu wasn't dumb by any means, she was one of the brightest minds in the demon slayer corps and she understood that the method Yuu talked about was theoretically possible.

"Yes, whether you believe me or not is up to you," Yuu said making Shinobu look at him with narrowed eyes.

"Is this your corps training method?" Shinobu asked since that seemed like the most logical answer, Yuu didn't have anything like their breathing techniques. So for his side to fight the demons they'd need something that could power them up.

'I have heard of a method similar to this before but the lack of evidence and proper proof dissuaded me from using it myself,' But now the proof was in front of her if Yuu was speaking the truth that is, Which he was.

"Yes," Yuu nodded without any hesitation.

"I see, so we are going to start this tomorrow morning?" Shinobu looked at the stack of papers in her hands that contained the schedule and explanation she had noted down. Yuu was also doing it since he wanted to get better than before, the past few days have been to warm up his body for the training that he will start from tomorrow.

'And this also serves as proof since I am going to be doing it alongside her,' Yuu thought as Shinobu waited for his answer.

"Yes, but how intense are the exercises going to be are up to you," Yuu said and Shinobu asked him a question on the spot.

"What level of intensity are you going to go for?"

"The worst one," Yuu said flatly.

"Same for me as well, I can't do anything below that," Shinobu had made up her mind.

'To catch up with him, I'll need to work extra hard, I can't waste any more time,' Shinobu was fully focused on getting stronger now.

"Alright, how much sleep do you get on a daily basis?" Yuu asked making Shinobu a bit puzzled.

"About 5 to 6 hours sometimes lower since we need to attend to the patients that come at night," Nevertheless she answered since it looked like it was an important question.

"You need to increase it to 8 hours, 9 if possible, otherwise your body won't be able to recover before the next day," Yuu said seriously.

"But I need to look after patients and Nee-sama is also injured," Shinobu couldn't really just ignore the patients that come in, they were her fellow demon slayers who risked their lives.

"I'll help you with the patients because if you don't listen to me you will end up joining them on the hospital bed before too long," Yuu didn't look like he was going to take any opposition on this.

'Damn bastard, does he ever get off his high horse?' Shinobu cursed in her mind as she couldn't refuse his words, she was able to understand the fundamentals behind the training regime and knew that Yuu's words weren't farfetched.

"I'll try to do it," Shinobu said.

"You 'Have' to do it," Yuu's words made Shinobu's eyes twitch.

"…Got it," Shinobu could only nod as she saw that he wasn't going to back down no matter what.

'He knows about this method better than me, so I'll need to trust him,' Shinobu thought shaking her head, though his tone did irritate her.

"Also get someone to procure all of the items we'll need right now, The day starts at 5 in the morning tomorrow, Don't be late," Yuu said standing up.

"Also don't expect me to teach you our methods just because you've done this," Shinobu said crossing her arms as Yuu looked at her.

"I don't need it," Yuu said walking back into the house leaving Shinobu alone in the backyard.

"Hateful Bastard," Shinobu cursed under her breath as the evening wind blew past her face.

"Next time, I'll protect you Nee-sama," Shinobu said looking at the setting sun before going back into the house as well. She still had many things to do.

***

The next day, in the morning at 5 A.M. Yuu and Shinobu were sitting in the dining room alone, they were the only ones who were awake now.

"Do I really have to eat all of this?" Shinobu was shocked at the amount of food on her side.

"You're going to need it for the rest of the day, so start eating," Yuu had already started eating already.

'Can he really eat all of that?' Shinobu blinked in confusion since Yuu's food was nearly thrice her portion.

Shinobu had helped Yuu make the food since she was unfamiliar with the dishes he made. There were a lot of dishes she saw for the first time like the weird yogurt with honey, fruit, and nuts in it. There was also bread but no rice which made her feel uncomfortable.

'Is this how they eat in the west?' Shinobu thought as she ate the food and in all honesty, she didn't like it one bit. The taste was too much of a change from her normal consumption.

"Are you giving up before even starting?" Yuu asked freezing Shinobu in place.

"Watch me, You Bastard!!!"