The bond between two siblings

Brutal training

Tanjiro pov:

As the demon who wore a purple kimono named 'kokushibo' said that he'll train me, i was confused, and when i asked why he would do train me, and why would he be willing to help me get revenge on my family, that was when his expression changed to a rather, sad face. And began to talk.

Kokushibo pov:

As my soon to student asked me why I'm helping him, I was sad, having to think about what i have done in the past, still hurts to this day. That's when I responded "though my sins in the past aren't forgiven, that doesn't mean I cannot do good things today, I guess i just want redemption for my sins" my student walked up to me and bowed in front of me "I'll be your student, and please help me, so i can get revenge on the man who slaughtered my family" as the boy was saying that he looked like he was going to cry, as I pat his head and responded "I will help you, and we both can get our revenge" as the boy looked up to me, wiping his tears away and asked "when does our training begin?" As i simply pat his head again and smash his head on the ground

Tanjiro pov:

I felt my new master pat my head, then moments later smashed my head on the ground, I was in so much pain "it begins now" kokushibo responded, its a good thing I have a hard head or the pain would've been worse.

Nezuko pov:

As our training began i was standing across what seemed to be a training ground, this first day I was going to be tested on speed, as kanao and I stood across kanae-san. We were both given a badge and placed it on our chest, the rule was whoever can get the badge off the person wins, and the second we began kanae-san immediately vanished, as i frantically looked around I saw kanae behind me holding my badge with a smile, I was shocked by how fast she was, but I remembered she was one of the hashiras. We did the same thing for 3 days to hone my speed, after that it was a match between me and kanao, we both stood across each other, and ran, i tried grabbing for her badge but she just side steps me and took my badge was i just landed face first on the ground. 'Ouch' then i heard a voice "Ara ara, try to be a bit more careful" it was kanae-san. As i just gave her a thumbs up as she still kept her smile. Then after that we did the same thing and though i have been able to get kanaos badge a few times, she got mine more than i caught her badge.

That was when kanae-san was teaching me about total concentration and how to use it .

Narrator pov:

As Kanae was teaching Nezuko about total concentration and how to use it, Nezuko has been growing so close to everyone at the butterfly estate. "Thank you so much for teaching me master" Nezuko was saying it with a bright smile Kanae simply replied "Ara ara, no need to thank me, and please, call me sister" when Nezuko heard that she looked like she wanted to burst into tears and immediately hugged Kanae. Kanae was a bit shocked but hugged back, at this point, Nezuko was like family to everyone in the butterfly estate.

While tanjiro on the other hand, he was growing close to kokushibo.

Tanjiro pov:

Kokushibo was training my reflexes, however this time we both were using our katanas, both kokushibo and we were using normal katanas for training. He has injured me a lot of times, sometimes even cutting off my limbs, luckily I was a demon, so they immediately grew back. However the first time kokushibo cut my arm off, my arm immediately grew back, as kokushibo just stood there, "you haven't eaten any human flesh, yet you can regrow your limbs pretty fast, impressive" kokushibo said, as i smiled at his compliment he immediately kneed my stomach, "Don't catch off guard!" He scolded me, while i was clutching my stomach while on the ground. "The way you swing your katana and the way you hold it is still like a 2 year old learning how to write! Now get back up you worm!"

This guy, is seriously, insane. For the next few weeks he has been teaching me total concentration, i was able to use the katana the right way now, and he also began teaching me how to use breath of the moon. So while we were having a spar, I finally mastered one of the many forms of breath of the moon.

Narrator pov:

While kokushibo and tanjiro was sparring, tanjiro used one of the many forms of breath of the moon. As tanjiro cut off kokushibos arm, and both were surprised.

Tanjiro pov:

"Breath of the moon, first form: dark moon, evening palace" I yelled immediately doing a horizontal slash on master cutting off his arm, and thats when I noticed, I finally was able to land a strike on master. I was overjoyed, and after master immediately regrew his arm he approached me and held my shoulders, he was proud, i can smell his emotions, as my sense of smell was that good, but my victory was short lived when i felt his arms grip on my shoulders get tighter and thats when i knew, I'm screwed. He immediately threw me behind him as I land back first on the floor hard. I may be a demon, but that doesn't mean we don't feel pain! "Thats for cutting off my arm" master responded while i was still trying to get up. After training with master, I immediately went to sleep, because though kokushibo only needed a bit of blood to fill his hunger and avoid eating humans, I on the other hand, I sleep! I do it to avoid eating human flesh. Though I haven't unlocked my blood demon art, I'm sure I'll be able to unlock it one day. But for now i going to hone my skills in breath of the moon.

Meanwhile at the butterfly estate

Nezuko pov:

Im still learning how to fully master total concentration breathing, and its been over a week now, kanao is still, kanao, for some reason she doesn't talk and uses a coin to help her make her decisions. And I am still in progress in trying to master flower breathing, because thats kanae-sans breath and she was still teaching me on how to use it. Shinobu on the other hand was training me and kanaos reflexes. And man she is a pain in the back. But between me and kanao, when we have our spar, it seems like were both at the same level of skill.  But it has only been a few weeks for me, and i need to hone all my skills if i want to find the man who murdered my family and took my brother, that 6 eyed demon will pay.

Kanae pov:

I was really proud of nezuko and kanao, and the both of them are family to me, i see them both as my little sister, just like shinobu. I made a promise that i would protect the people at the butterfly estate since they were all like family to me and family must be there for one another. But something is still off about the time nezuko encountered the demon who took her brother, if he really was the one who killed her family, then why did it leave nezuko alive? But thats a mystery for another day, for now, i want to rest.

Tanjiro pov:

Muzan has summoned master to a demon meeting, and i took this opportunity to take a quick look outside, however it was day time and the sun had burned me a little, realizing I wont be able to find nezuko now, but maybe some time later when i master all the forms of breath of the moon. 'One day nezuko, I'll meet you again'

To be continued

Hello! How was this chapter? If there are anything else i should add let me know!

Keep in mind I'll try to post daily. Im not sure how many chapters per day. But please enjoy the story!