Chapter 2

In the Kendo Club, Ace was observing all the female students swinging their shinais seriously and in sync. As they moved one could see a certain unique rhythm to their moves, transpiration in their foreheads as they concentrated in their actions.

"Focus on your breathing, especially you Aoi. Your breath is starting to slip." Ace said as he pointed to one of the girls who flushed a bit and corrected her breathing.

Nodding he looked at the girls for a while longer in satisfaction. His nose twitched as he spoke to a corner of the room.

"You two perverted idiots, get out of here or I will let the girls beat you up, or maybe you would rather I do it?" Ace said with some venom in his tone, hating these two.

As he spoke thus, the sound of feet scrambling away could be heard as Motohama and Matsuda ran away from their hiding spot. The two feared Ace more than they feared mostly anything else by this point and did not want to experience any more of his beatings.

He was simply too merciless with those two after Motohama invited Isane for a date. The girl was so happy for it, only for during the date he try to force her to kiss him and try to feel her under her skirt, all while saying all sorts of nasty and inapropriate things to her including how he promised to later 'share' with Matsuda and how a girl like her would live to feel their 'huge' shafts.

Needless to say, Ace, who was guarding her in secret just to make sure that the famous pervert didn't try anything that Isane wasn't comfortable with, did not take kindly to the boy's tone... or how he just couldn't take a 'no' for an answer after she pushed him away three times as he tried to kiss her and feel her breasts in public.

After that incident and seeing how shaken up Isane got from the whole experience, Ace became much more protective of Isane. Thankfully she soon recovered from the ordeal and returned to normal, but even so Ace would always make it a point to be around in case she gets a date to at least make sure a repeat doesn't happen. And of course, Ace also made sure to make Motohama and Matsuda feel true fear as they never again tried anything to Isane.

Shame that they never truly stopped acting pervert with all the other girls they can despite the many beatings and Ace showing their parents evidence of what the two did on a regular basis.

Sighing at the fact that he belonged to the same species as those two failures of Darwinism, Ace looked at the girls practicing arduously. Nodding in approval hed spoke up.

"That is enough. Let's change to sparing practice. One at a time against me, let's see your improvement."

One might find it strange that Ace was acting as if he was the instructor here, but after learning all the breathing techniques from Kimetsu no Yaiba he was already a great expert with the blade, only lacking actual experience with using the blade.

The first girl appeared in front of him, it was a diminutive blond with short bob hair, her face serious as she looked at him before taking a deep breath and moving towards him.

Avoiding her strike he countered and she started to move as well. Soon they were moving at speeds higher than regular humans had any right to move and Ace disarmed her.

"Very well, your breath has improved and your handling of the blade is coming along nicely. You should pay attention to your footwork though, it was too rigid." Ace pointed out and the girl flushed, nodding her head and moving along so the next could come up.

If the devils were present they would have been shocked by the display, but even more so when every single member of the team presented skills beyond normal humans one after another. This was something Ace had done after joining the club the previous year, not wanting to be in a team that would lose matches he made a deal with the club members.

He would instruct them about swordsmanship but they were not allowed to teach or show what he taught to others nor could they go all out unless it was absolutely necessary to win a match. In exchange, they would give him all the money they had on hand before any official match and he would bet with it, if they win he would get a cut of the winnings and if they lost he would pay back their money for them.

It might sound stupid, but the girls in the club agreed since there wasn't really any harm in doing this in their eyes since they wouldn't lose any money as the only one taking a risk was Ace. Besides, if they could learn from Ace's swordsmanship which was clearly above theirs, then all the better.

After training with Ace they never lost a tournament since.

In all of them since that moment, not one of the members lost since Ace taught all of them the basic breathing technique used by all the common demon slayers in the demon slayer core. Don't look down on this, it might be the weakest breath style, but it could still increase their reflexes and attributes by three times over, if you then add Ace's teaching in swordsmanship they all became true pros.

However, as the final two approached the others took a few steps back, not wanting to be close now.

"Ace-kun, can we do as usual?" Murayama asked in eagerness. Her chestnut hair in a simple ponytail danced behind her as she looked excitedly at Ace.

"Yeah, otherwise it would be quite unfair." Katase said, her short pink hair waving as she went into her sword stance taught by Ace.

Ace, seeing these two, sighed a bit at their eagerness before nodding.

"Fine, you two can come together. Show me your progress." He said as he too entered a stance.

Katase, who was in position, went first.

"Thunder breath, first form: Thunderclap and Flash."

Suddenly, with an explosive speed that could make even a knight blush in defeat, Katase striked at Ace.

The speed was blinding, however-

"Sun breathing: Burning bones, Summer sun."

With that Ace unleashes a large circular slash that defends from the imminent frontal attack. The swords clashed and Katase was flipped over, ending up going to the opposite wall of the room.

Not letting the pressure Murayama moved as well.

"Water breathing, third form: Flowing Dance."

Murayama swings and bends her blade in a winding motion along with her body and dances in a flowing pattern, trying to slice everything in her path.

Ace, seeing this, began to use another move.

"Sun breathing: Dance."

With that, the two turned into a whirlwind of movement that normal humans would be hard-pressed to see, but the rest of the club with their improved reflexes from the basic breathing technique which enhanced their basic senses to beyond normal humans.

Katase, on the back, also moved along, using the wall she was sent into as a springboard as she dashed at the pair dancing with blades.

Murayama, already used to her friend's way of acting, opened a path for her by stepping aside while using her blade to knock Ace's sword up.

"Thunder breath, second form: Rice Spirit."

Five sword strikes at speeds like lightning descended at Ace who barely managed to avoid them, truly appreciating how the thunder breath's explosive speed couldn't be beaten by other styles. Even his Sun Breathing was a tad slower, just like it was less fluid than the water breathing of Murayama, or less physically strong than the Stone breath, but the sun breathing was still the most comprehensively strong of the styles as shown by Ace avoiding their strikes before he retaliated with a powerful trust that needed Murayama to divert from Katase's way.

Ace was much more physically fit than both girls due to his contracts over the years, but he controlled his strength as to only be around the same level as the girls that he took as personal disciples, as such their spar was not so one-sided. In the end, their battle continued for a good fifteen minutes when the two no longer were able to keep up and stopped the match. Their bodies and breath having reached their limits.

Seeing this Ace stopped his moves as well, whipping some slight traces of sweat from his face as he smiled proudly at these two who advanced so much from their start.

"You two have done amazing progress, congratulations."

The two just smiled at their master.

... No, he did not buy them despite his essence allowing him to do so.

The price of a person changes depending on a few factors. Innate potential, current ability, connections, and their personal feelings towards Ace. Murayama and Katase already had a deep crush on Ace since Middle School, not only that, they were just normal humans without any important connection and their innate potential was quite poor if no one helped them, so their price was the cheapest amongst all people Ace knew.

However, he never bought them for fear of how this might change who they are. He would only buy someone if the other party was an enemy as to see how it works or if it is needed (he wanted to test if buying someone from another world means they are brought over to his own world).

Instead, Ace and the two were now in a master/disciple relationship, the two girls's talents were simply better than those of the rest of the club and he actually liked them enough to spend the extra time to help them learn. Giving the two the breathing techniques would at least be a way to make sure they would be safer if something happens instead of just being a helpless civilian in the future.

After they made a deal regarding them turning into his first disciples, Ace would go one step beyond the rest of the club by explaining to Katase and Murayama what he knew of the supernatural to a degree. That impressed in the two teenagers the need for strength and both were now dedicated towards training. The two were now at least as strong as a low class knight while still being fully human and without a powerful weapon, bullshit bloodline, or the help of any energy besides their own bodies. If either devil heiresses found out about these two there would be no way they wouldn't scramble to try and snatch them into their peerages.

Seeing the two's exhausted expressions with sweat running down their faces and making their clothes glue to their skin, he could see how unwilling to move they were, probably wanting to just lay there to rest for a bit. Ace's heart moved a little as he smiled and said.

"How about we go eat something tonight? I heard there is a nice pizza parlor that opened in the sixth street and I was interested in checking it out."

"YES!" Katase said, raising her arm tiredly, her muscles screaming at her as she did so.

"We will be there." Murayama said with a tired smile, her breathing ragged as she did so.

Seeing this Ace sighed, knowing that the time for him to show his actual capacity for the two heiresses was approaching, he still decided that he might as well help the two girls up.

Bending over, he took one girl in each arm and raised them. The two basically held by his arms as if sitting on him, his hands holding onto her legs for support as he carried them to the showers. The rest of the club followed and after he sat both blushing girls down on a bench of the showers he left, confirming the hour for them to meet later.

///---///

In the back of the school, Sona, Rias, and their respective peerages were waiting for Ace.

"Sona, are you sure he is coming?" Rias asked, noting that it was already over twenty minutes from the agreed time.

"He said he would, perhaps we should send someone to go find him?" Sona proposed, not really thinking this as such a great idea

Rias thought for a bit before waving her hand in the negative.

"We can wait another ten minutes. I just hope he is worth the wait."

Rias herself was quite excited and a bit vexed. A strong person was right here already in school and she had no clue about it for the whole of last year. If she knew she would have already tried to approach him since the previous year, but now that the time limit for her was approaching this was truly the ideal time for it.

As for the conditions Sona said he had to join a Peerage, Rias honestly wouldn't mind as long as he agreed to help instantly in case of danger of the life of hers or the rest of the peerage. Payment for it can be agreed upon later then. The money wouldn't be an issue for her at any rate, her family was obscenely rich and if he wanted it then he can have it.

This was not a feeling shared much by Sona who was not as desperate for strength as Rias as she care more about her peerage working well together instead of individual power, and someone who was as individualist as Ace wasn't so appealing for her. That was why her peerage lacked anyone with immense potential like Rias' peerage members, but their ability to work together as a team could not be matched even the slightest bit by Rias.

As the two were talking Ace finally showed up. Wild wavy black hair, black eyes, a tall musculature, and freckles on the cheeks.

"Sorry for the wait, the club took a bit longer than expected." Ace said as an explanation.

After a bit of an awkward silence, Rias said.

"Well, you said you would accept joining either of us and you wanted to show us what you can do. Do you want to show your sacred gear, perhaps?"

"Nah, I didn't unlock that yet. No clue what it is." Ace said as he started doing some light stretches. "I am good at alchemy and swordsmanship, you can decide what you wanna test first."

Rias was slightly shocked at those words but someone had already stepped forward.

"Kaichou, let me test his swordsmanship." Sona's only knight, Tomoe Meguri said earnestly. She was usually the one that admonished Ace whenever he did something wrong and a chance to put him in his place sounded perfect for her.

Sona thought about it for a moment before nodding her head.

"Very well, my knight will help test you in your swordsmanship." Sona said as Tomoe moved to in front of Ace.

Ace, seeing this, tilted his head to the side and spoke.

"... Is this enough?"

Tomoe, putting on a confident smile, spoke up.

"Don't worry, I will not go too hard on you."

Ace, hearing this, chuckled a bit. After the exchanges he did over the years and with his mastery over the Sun Breathing technique, he fully believed he was at least equal to a Hashira in battle. With more battle experience he would be confident he would be at least as strong as Gyomei even, so how could Tomoe compare with him?

"Well, I hope I don't disappoint. This is a job application test, after all." he said as he took out his sword just like Tomoe did. There was already a magic field around to isolate the two sides so Ace was not afraid of creating too much noise.

Tomoe darts at Ace using her speed as a knight, Ace eyes are fixed attentively at her as he tried his best to evade her strikes with minimal movement. He didn't start using his breathing styles instantly, curious to know how Tomoe's fighting style was exactly.

After a while of fighting Ace had a clearer understanding of it. In honest terms, she had speed and strength befitting of a knight class devil, but her 'style' of swordsmanship could be seen as just a single step above flaying around with a blade and hoping to hit. It was honestly quite disappointing for Ace, seeing someone with such speed and power but so poor actual control of the blade. Heck, her control of the sword was even worse than the one that the regular members of the Kendo club had, even the worst of the club was still a step above her.

Feeling that using Sun Breath on someone on this level was simply not worth it and would likely kill her accidentally, Ace changed to another style that would be less certain of separating her head from her neck.

A sound like the rushing wind could be heard as Soma moved to attack.

"Wind Breathing first form: Whirling Cutter."

With the wind breathing Ace's speed increased to beyond what Tomoe could reach, Ace dashes forward at blinding speeds and slashes continuously in a horizontal cyclone pattern, Tomoe getting cuts and scraps all over from this move until her sword is knocked up and her eyes widen as Ace's sword stops inches from her neck, ready to decapitate her if needed.

Soma's current body fitness was in truth not much better than those of a low to mid class devil, but never forget the boost that a breathing technique could give to its user. Just based on this his speed and strength while using a breathing technique was already at the level of a High Class devil that specializes in the body.

Tomoe, who was currently just a normal low class devil, couldn't match him whatsoever.

Ace, stopping his breathing style, felt some slight aches as he furrowed his brows. Using a breathing style he was not overly used to was not that great an idea, it seems, but he still wanted to try it.

The five breathing styles of Wind, Flame, Water, Rock, and Thunder were created from the Sun Breathing, but they all evolved since then so perhaps by understanding all those styles he could create his own style in the future. He had the time to see if such a thing was possible anyway, and being more versatile in how you fight wouldn't be a bad thing at any rate.

With such a swift and decisive defeat, the uninterested look of Sona slightly changed while Rias's eyes shined. Such a strong swordsman would certainly be a great help for her peerage.

Ace then put his sword back in its sheath.

"... Your sword technique needs a lot of practice. There is more to swordsmanship than 'sticking others with the pointy end'."

Finishing with reprimanding this girl Ace returned to in front of Rias and Sona and said.

"Now, about my other skill, who will help 'test' me?"

Hearing those words, Rias and Sona noted something that, with the display they just seen, they almost entirely forgot.

Soma wasn't only able to use a sword, but also 'alchemy'.

They were not exactly sure what that would entail, so they were not too sure on what to do.

"Buchou, let me do it this time around." Akeno said, stepping forward.

Rias, hearing this, understood. For the sword test, it was one of Sona's peerage members that fought with Ace, as such for the magic/alchemy test, it should be someone from Rias' peerage. However, with there only being three that could do it, Akeno was the best option since Kiba was only good with swordsmanship and Koneko was only good at hand-to-hand combat.

Rias agreed to this and so did Sona who was more interested in what this alchemy represented over swordsmanship.

Akeno, stepping in front of Ace, gave him a beautiful smile.

"Ara, ara, it seems like this onee-san will have to test and see how strong you are. Do try your best and entertain me." Akeno said as she released her devil wings. "Don't worry, when you can't handle it anymore just say the word and I will stop... eventually."

"It is funny that you said that, I was about to say the same." Ace said with a smirk, a yellow magic circle composed of several hexagons with a symbol in the middle appearing in front of his hand and a blast of thunder being sent directly at Akeno.

Seeing this she quickly evaded by flying up before launching a strike of her own. Ace did not falter and another circle appeared around him, this time in blue as water was erected all around him in large quantities.

"Water? You used water to defend against my thunder?" Akeno asked incredulously.

"Naturally." Ace argued. "This is pure water without any impurities, it is one of this world's best electrical insulator materials. As such, it works wonders to defend against electricity without anything else added to it. Now, let's try this."

As he said this the water that was being used as a barrier changed and advanced at Akeno, turning into the figure of a dragon hunting her down.

This was something Ace developed when he examined the alchemy understanding of both Carol and Bavarati Illuminati, Carol could easily produce large amounts of substances as well as interfere in concepts while the Illuminati were great at controlling matter as well as the manipulation of space, combining the two was an extremely powerful thing to be done.

Without another option, Akeno could only move higher to avoid the dragon. Taking advantage of her height she used the electricity present in a cloud nearby to send a powerful bolt at Ace.

Ace used another yellow circle, releasing a thunder of his own but instead of being to counter Akeno's strike he just used it to direct the electricity directly to the ground, dispersing it without causing any damage to Ace.

Seeing the location Akeno was at he opened a new circle after he finished redirecting the lightning, the new circle this time was green, a tornado surged from it, trapping the flying Akeno inside. Not giving her a moment Ace used a second alchemic circle, this time red as a torrent of fire was released into the air, the two working together to create a fire tornado with Akeno inside.

This, however, was Ace's limit. He was just a human and his magic reserves were nothing that great, while the alchemic techniques were extremely cost-effective he didn't have more magic than what he already spent by now.

As he was about to disperse the circles, a blast of power of destruction hit the tornado directly, destroying the reaction happening and finishing the attack.

This was naturally done by Rias who no longer could hold herself back from rescuing her friend that was in danger. While the temperature of that tornado wouldn't be enough to kill someone of Akeno's resilience and power (she was, after all the daughter of a 12 winged fallen angel) it was more than enough to injure her.

Akeno fell to the floor but was caught in time by Rias who flew to catch her best friend. After seeing that she only had some light burns Rias was relieved and then turned to Ace.

Rias's expression was slightly complex, while she was excited about the prospect of someone like this coming to her side, she also did not like the idea of her cute servants being injured in any way. Swallowing her complaints she approached Ace just as Sona did.

"Mister Hyoudo, I believe that perhaps your terms can be agreed with." Sona said before Rias could speak.

Sure, his terms were by all rights quite absurd for a king to accept, but his power was clearly shown and his potential can be well imagined, ignoring such an asset out of hand just because of some inconveniences was not something Sona would do. Sure, she would lack the same degree of control with him she had with the rest of the peerage and she would need to give monetary payment for him, but it would be well worth it since she felt he might be able to help her achieve her dream.

If she wanted to build the school she desired she did not simply need the recognition from her academics and position as heiress, she needed martial might. Devils only truly respected power and strength, her peerage lacked any true heavy hitter and Ace could be just what she needed.

However, Rias would not let it go and spoke up just as well.

"Sona, don't try to take this one from me. We both know that I have a more urgent need and I fully agree with the terms he proposed. As long as he can help me with what I need, I don't mind those terms at all." Rias said, causing Sona to frown.

The two were about to argue when Ace stopped them.

"Well, since both of you are willing to talk business, how about you each propose a deal with me and the most appealing I will accept. Those terms, after all, were just the basics. We haven't even talked about initial salary, bonuses, vacation, and other such important aspects."

As Ace said this Sona and Rias realized, this guy was an extremely greedy person to the bone, if they wanted to move him they would need to give him something worthwhile in return. Looking at one another, it was possible to see a fierce competitive spirit shined in Sona and Rias's eyes, both not wanting to lose to each other.

Meanwhile Ace was wondering who would give the best benefits and if it would be enough to open another world for trade. If he wanted to unlock worlds with cash he needed to spend around fifty thousand dollars for the next one, with each new one rising the value by 25 thousand, and he can only unlock at most two new worlds every week. He had accumulated 27 thousand over the years but with some luck, more money would be coming in after this.

And, in the back, a small yellow bird was watching all the procedures. In a flash of flames it vanished, it was earlier than the usual time for reports but this time's information was just too important. As the only familiar of the little princess of the Phenex house, it naturally had to come to report.

///---///

AN:

First and foremost, Merry Christmas and happy new year. I will take a short break of two weeks for IRL vacation and new year matters, but I hope you guys enjoyed this chapter.

So, what do you guys think? As a pure human who had no access to a sacred gear or a unique bloodline, he reached a level honestly no worse than the current Sona or Rias in combat, probably higher. And that is just his base most ability, when he unlocks his gear and after turning into a devil, well...

Sairaorg will have competition for the position of the strongest young devil.

Next, Murayama and Katase are now Breath users from Kimetsu no Yaiba. And strong users at that! They are around as strong as Tanjuro was during the fight against the Lower Moon 6, but with plenty of room for growth as they are still normal humans now and they also lack a strong weapon.

I have so many ideas about things we can do. For instance, let Ace unlock his Aura from RWBY as to let him unlock it to others as well. There are a lot of possibilities, hells I was even considering having Ace train someone into a mecha fighter, Gundam or Knightmare style.

Anyway, we now have three routes we can take. Join Rias, join Sona, or join Ravel.

Yes, Ravel IS an option. She should be High Class at any rate and if we go with her he could be her Queen. Yeah, he demands money for anything besides the protection of her and the rest of the peerage, but she is a Phenex.

Money is the one thing she would never lack. They are a good match overall. If he joins Ravel, so would Isane, him as Queen and Isane as the eight pawns. Rias, Ace can always produce the Autoscorrers to be her pawns, which would be more than enough to deal with Riser I am sure.

Well, we will have to see where this will go next I guess.