The end result? I lost.
Well, I wasn't using my full powers and I restricted myself to just using the first firm of my breathing style.
But still, I held up pretty well against Shinobu and was able to fight with her for more than 30 minutes before my technique faltered.
After my loss, I realized something though, there was a big flaw to my one handed sword technique, it was impossible to sustain in a long battle.
I was overworking my left hand whilst my right hand was only there for balance, so, I figured that I could teach myself the same techniques I used for my left hand and use them with my right hand.
And this combined with the fact that I had agreed to teach Kanao, it was a perfect scenario really.
After our spar, I had gone to sleep on the roof, but soon afterwards, I saw Tanjiro and Shinobu talking in the training ground.
Shinobu was probably telling him about total concentration constant right now, and how Kanao had to break gourds with just her breath.
Trying to ignore their conversation, or well, Shinobu's flirting, I just couldn't stand it anymore and unsheathed my sword loud enough for them to hear me, before making a sleeping gesture with my hands and pointing them inside the house.
Seeing this, Shinobu just chuckled whilst her hand covered her mouth before leading Tanjiro back into the house.
Watching them go, I finally relaxed and lied back down again.
Thinking for a little while, I now had to accept that the canon had changed irreversibly now.
With so much changes, I knew that being powerful would be my only guarantee for the future.
Thinking about the training that I would subject myself to along with Kanao, I just smiled, before falling asleep.
…
Waking up early the next morning, I entered the forest surrounding the house and found Kanao at our appointed location, a huge rock jutting out from a hidden lake.
Seeing that she had a chokuto in her hand, I smiled, thinking that Shinobu really was considerate of her disciple.
Taking out a sheet of paper, I wrote,
"I'll demonstrate the move we'll be practicing today, and then we'll both practice it until we master it. You see, my breathing style starts needs a very strong and sturdy foundation, so we will both practice this move until we get it perfect at least 1,000 times in a row."
Reading the parchment, Kanao's eyes widened, but then narrowed in determination.
Seeing this, all I could think was that her coin held a considerable amount of power over her.
Well, anyways, I took out my chokuto and demonstrated the move, a simple unsheathing and resheathing of the chokuto whilst only using one hand, slowly of course, so that she could see what was happening.
Then, after seeing it just once, she surprised me by attempting to do the move, and succeeding about halfway through almost immediately, before failing, as some miscellaneous movements destroyed the flow of the move.
Seeing her early success, I immediately tried it myself with my right hand.
And well, I failed too.
But, due to my experience, I was able to succeed about two thirds of the way before failing.
But, of course, I knew from experience that getting this far still meant that I had to iterate the move about 1,000 times more before it became perfect.
So, the both of us standing on the flat rock overlooking the water, we started practicing, dropping our chokutos and picking them up from the water whenever we dropped them, retrieving them immediately with our superhuman reflexes as we didn't want them to sink to the bottom of the lake.
Also, I was always looking over at Kanao, making sure to correct anything that I saw was obviously bad to her posture, and like the prodigy she was, she was able to absorb the information almost perfectly.
And finally, at the end of the day, I was able to get in 300 perfect renditions of the move whilst Kanao was able to get in 150 perfect renditions of the move.
Resting on the rock as night fell and the moon rised, I just stared unblinkingly at the water.
Kanao sat next to me, and we both meditated until the moon was at its peak.
At this point, I knew it was time for her to rest her body, especially her arm after working so hard today, so I awoken her from her meditation and we ran back to the mansion.
Writing to her to get a massage before she went to bed because I didn't want her to be sore for tomorrow, I then wrote a simple goodbye and then jumped onto the roof.
Looking at the full moon one more time, I closed my eyes and drifted off to sleep.
...
Waking up at the same time, I moved to the lake.
Once I reached the rock and saw that Kanao was already there, I didn't waste a single second and started warming up.
Seeing this, Kanao also warmed up and then we started renditioning.
Well, unfortunately for me, even after the warm up, I wasn't able to do a perfect rendition of the move, so I had to start over at one.
On the other hand, Kanao was able to easily continue where she left off, but I soon caught up to her again.
Finally, by midday, we had both completed 1,000 perfect renditions of the foundation of my whole breathing style.
Now, it was time for her to learn about the actual "breathing" part of the breathing style.
I took out a long piece of paper this time, and then I started writing furiously.
Finally finished with compiling all the instructions for the breathing method, I let her read it, before performing it for her to see.
You see, this was my own take on total concentration breathing. Taking the idea of filling each cell with energy, I instead imagined the sun's energy filling my cells during the day, and the energy of the billions of stars in the night sky filling my body at night.
This allowed me to continue to use the breathing style no matter the environment or time of day, as I knew the sun would always be there in the sky even if it was cloudy, and I knew the stars would always be there even if the moon shined brighter than usual and eclipsed the stars in the night sky.
Using this method, I effectively filled every single cell in my body with the energy of the stars, both old and new.
And this was the source of my power.
After showing her how it was done, including the intricacies of some things like the position of the muscles and bones in the body whilst one practiced this breathing style, she started practicing it herself.
I would look over her, and then adjust her body every time she was doing something wrong.
Of course, there was only so much that I could do, as the rest of it relied on her imagination to bring the stars' energy into her.
By the time night fell, she still couldn't do it, but we continued through the whole night.
Finally, after 5 straight days of practicing the breathing style, she got it.
She truly was a prodigy with a great sense of determination, a true monster.