3rd POV. Yoshiwara District.
Upon witnessing the horrible destruction caused by the Upper Six siblings....
Akito assesses the wind for the situation.
Akito: It's already worse than it possibly is.
Akito: Tengen-san got a major injury. Inosuke is also in great danger......Zenitsu is trapped....
Akito: Tanjiro......
Akito: Damn it! I need to hurry!
Akito traverses the destruction, flames raging on, smoke rising upon the sky....
Akito: *cough* *cough*
Akito: Mother Nature is going to be so sure to reclaim this part of her domain once everything is over.
By navigating through the flames and debris.....
Akito: Where are they!? The smoke is obscuring my vision.
Akito: Still......
Akito: We need to find a way to behead the siblings.
Akito: If we can't do it at the same time, then prevent the one of them from reattaching their head.
Akito: Then, I'll have to find a way to prevent the elder brother into getting into my way......
Akito: Or the other way around.....
A few moments later.....Akito sighted Gyuutarou, kneeling in front of Tanjiro whose face is looking upon the sky, while the demon mocks.
Until.....
Tanjiro headbutts Gyuutarou and even knocking him off his feet. He used the opportunity to sever the demon's head.
Akito: Then.....! I'll take care of the sister!
Daki extended her belts to attack, but was intercepted once more by Akito.
Gyuutarou: You—
Tanjiro: Kaedehara-san!
Daki: How are you still alive!?
Akito: ........
Akito: I'll take care of the sister!
Akito rushed towards Daki and he began to decapitate Daki, but she stretched her neck and it became soft.
Akito: It bends yet hard! Even with my red blade!
However, Zenitsu soon followed up.
Zenitsu: Thunder Breathing, First Form!
Zenitsu: Godspeed!
Zenitsu joined Akito to decapitate Daki and increase the speed.
Daki: !?
Akito: Zenitsu!?
Zenitsu: I'll take care of the speed, senpai! Just focus on pouring all of your strength!
Akito: Right!
Zenitsu: LET'S DO THIS, SENPAI! THIS IS THE CHANCE THAT TANJIRO CREATED FOR US!
Akito: YEAH!
Akito: Blood Demon Art!
Daki: !?
Akito: Leaves of Death!
Akito used his blood demon art to coat Zenitsu's blade to increase his power which is evident by the leaves that is swirling around the Thunder Breath User.
Zenitsu: Such power........!
Zenitsu: But I won't be able to hold on like this! I already used Godspeed when I escaped the rubble! Then when I synchronized my attack with Kaedehara-senpai.
Zenitsu: Kaedehara-senpai is also pouring all of his strength for this!
Akito: We got to hold on! We're almost there!
Daki: I'm going to chop you two into pieces before you can decapitate me!
Daki attempts to cut the two from beheading her by slicing them up with her belts.
Akito: I'm the only one who can block and deflect these belts! If I do that, then......!
Fortunately, Inosuke arrived to tore the belts and even kept up with them.
Daki: !?
Daki: Why is he here!? Onii-chan stabbed him through the heart!
Inosuke: Don't underestimate the flexibility of my body! I can shift the position of my internal organs as if it's child's play for me!
Inosuke: Since I also grew up in the harsh mountains, poison doesn't work on me!
Inosuke also uses his sword to decapitate Daki.
Akito: Okay! Now I can pour all of my strength entirely!
Akito's sword begins to turn into crimson and a maple leaf mark appeared on his right hand, with ukiyo-e wind patterns connected to the leaf.
Akito: We'll finish this off! Tanjiro, Tengen-san!
Daki: Onii-chan! Do something, will you, onii-chan!
While Tanjiro and Tengen are also in the process of beheading Gyuutarou....
The five demon slayers, pouring all of their strength to finish it all.
Akito: AFTER CENTURIES........WE'LL CHANGE THE COURSE OF HISTORY!
Akito: WE WILL CREATE HISTORY! TONIGHT IS THE NIGHT WHERE THE UPPER MOONS WILL WANE!
Akito: Blood Demon Art!
Akito's blade began to glow brightly green that fades to yellow, orange, and red.
Akito: Shinken Battou! Kusanagi no Tachi!
Pouring all of his strength to make the final push, Akito alongside with Zenitsu and Inosuke, have finally beheaded Daki.
At the same time, Tanjiro also beheaded Gyuutaro's head.
After centuries, the tides have finally changed.
In the Ubuyashiki Estate, Kagaya, who is now bedridden, sensed the resonating victory against the Upper Moon Demon.
Kagaya: Ah......they defeated an Upper Moon!?
Kagaya: Finally......!
Kagaya: He brought forth a miracle!
Kagaya: Good job Tengen, Akito, Tanjiro, Nezuko, Zenitsu and Inosuke!
Kagaya: *cough* *cough*
Kagaya coughed out blood as he tries to sit up, he is supported by his wife, Amane.
Amane: Kagaya-sama.....
Kagaya: For a hundred years......
Kagaya: For a hundred years nothing has changed!
Kagaya: But now it has!
Kagaya: Amane.....*cough* *cough* *cough*
Amane: Yes?
Kagaya: I always knew Akito would bring a miracle! He brought forth a miracle!
Kagaya: And with the miracle that he brought forth, fate is about to take a dramatic turn!
Kagaya: The son of the demon who betrayed Muzan.......
Kagaya: The victory that he paved for his comrades will spread like a ripple!
Kagaya: Sweeping up everything around them, shaking them to their core!
Kaguya: And finally, it will reach that man.
Despite his the worsening condition of his illness, the Master of the Demon Slayer Corps lets out his resolve.
Kagaya: Kibutsuji Muzan! We wull defeat you without fail during our generation!
Kagaya: You, the sole blemish on my family!
Kagaya: *cough* *cough*
Kagaya continued to cough out as Amane called to her children to fetch their father's medicine and towel.
Meanwhile......
At the aftermath of the battle......
Akito landed on top of a roof, not far from Inosuke and Zenitsu. Using all of his strength to conjure up such a powerful attack, Akito is about to pass out from exhaustion.
But before he did, he sensed the wind, giving him a warning.
Akito: !!!!
With his instincts kicking in, and pouring the remainder of his strength.....
Akito used his demon powers to create a mystical barrier to defend himself and his allies from the multiple blood sickles that bursted out from Gyuutarou's body.
The barrier barely held out before the building they landed on crumbled. Akito was knocked back a little bit in maintaining the barrier and was separated from his group.
............
A few days later.......
At the Butterfly Estate.......
Akito finds himself inside the room.....
He slowly opens his eyes to adjust his vision, and when he pans his sight to his left side, he saw his betrothed, a sleeping Mitsuri.
Akito: Ah, I'm back......
Akito: How long was I out......?
Mitsuri woke up.......when she sat up, rubbed her eyes, and saw Akito awake.
Mitsuri: Akito.......
Akito: Mitsuri.....I'm back.
The Love Hashira jumped to embrace her beloved, crying with tears of joy and relief to see her fiance, safe and sound.
Mitsuri: I'm glad that you're alive and well....!
Akito: Don't worry.....I've cheated death many times now.
Mitsuri: But it doesn't mean you have to be so reckless!
Mitsuri: Still, I'm glad that you came back to me, safe and sound.
Akito returned the gesture.
Akito: Mm.
They parted and Akito asked Mitsuri about what happened.
She told Akito that he was out for at least five days. Shinobu was concerned that despite receiving only minor injuries, she observed signs of extreme fatigue upon Akito.
Kyouko theorized that because of Akito's dual nature of being human and demon, his human side can't completely compensate to the taxing effect of using his blood demon art.
Despite his two natures already balanced, exerting too much power is still costly.
There is no lethal danger from that condition as Akito will eventually regenerate his stamina. But when using his full power to exhaustion, his regeneration is temporarily halted and needs a normal treatment.
Because a remainder of his power will focus on regenerating his stamina, the most effective way to this, is the method that Nezuko is using to recover her strength, to sleep.
Thus the reason why Akito was out for five days.
Akito: I see. How's my mother?
Mitsuri: Mother is currently at the Kaedehara Estate, taking care of Father.
Mitsuri: Mother sensed your victory against the Upper Moon. She sent a crow to call on the Kakushi to help with the evacuation of the Red Light District and tend to the wounded.
Mitsuri: She's also the one who personally brought you here.
Akito: I see. What about Tengen-san?
Mitsuri: He retired. He said that he can't fight anymore.
Akito: Considering his injury. It's reasonable.
Mitsuri: You finally defeated an Upper Moon.....
Akito: Yeah, I know.....that is only the proof of how far I've finally come.
Akito: At first I was barely able to hold on my ground against Upper One.
Akito: But I still have to exact justice upon Masato's death.
Akito: I'm not yet strong enough.
Akito: For now, I have to rest.
Akito: And I need to train.
Mitsuri: I'll help you with your training!
Akito: Thanks, but this training doesn't require physical strength.
Mitsuri: Doesn't need physical strength?
Akito: I need to further resonate with my power. My blood demon art.
Akito: Just like Nezuko's flame that can negate another blood demon art.....
Akito: Mine is exactly the same, to counter demons.
Mitsuri: So, you'll train with Mother?
Akito: Yes, I have to. Though I have full control of my powers.....
Akito: The backlash is still too great. I need to become stronger and find a way to counter these backlash.
Mitsuri: But you need to rest, Shinobu-chan said so.
Akito: I know. With the recent events.....
Akito: I have to improve further.
Akito: What about my father? How is he?
Mitsuri: He probably wouldn't last long. When I visited him a few days ago, he's already bedridden.
Mitsuri: He can still speak, but his strength is fading each day.
Akito: His illness is catching up to him.
Akito: I guess I'd better be there for Father, we may never know when his day will come.
Akito: This will also give me time to train as well.
Akito: What about the other three? My kouhais?
Mitsuri: Ah!
Mitsuri: Tanjiro-kun is critically injured. He's still out. Zenitsu-kun on the other hand, his legs are.....totally injured and he won't be able to walk for a while.
Mitsuri: Inosuke-kun on the other hand, they said he was poisoned during the fight.
Mitsuri: And he's still being treated as we speak.
Akito: Inosuke and Tanjiro are the ones really most injured and poisoned.
Akito: Tanjiro's serious injuries, Inosuke getting stabbed and poisoned....
Akito: .......
Akito: But I'm glad that we're all alive and well.
A few days later, Akito finally made a full recovery. But he requested to be on leave for a while.
His reason is to further train his powers, and to take care of his father whenever his mother is away on a mission.
Kaedehara Kyouko became a part of the Demon Slayer Corps and was providing vital intel to the locations of demons, and where they are usually spotted. Because of this information, the number of demons began to dwindle considerably.
During this time, Akito continued his further training of his blood demon art. His mother taught Akito how to intricately use his power in order to increase the quality of his power without receiving any further physical backlash.
And now, two months have passed.....
Tanjiro eventually woke up from his coma.
Akito was still training when he received the news and he visited Tanjiro.
A week later, Tanjiro made a full recovery and began to train with Akito at the Butterfly Estate or to the Kaedehara Estate.
Tanjiro finally met Kyouko and Hiromitsu. Tanjiro was amazed by Kyouko being a demon immune to sunlight.
Kyouko also learned about Nezuko's condition and decided to train her to use her powers and control them.
Kyouko was even amazed by Nezuko's abilities. She even theorized that Nezuko may also conquer the Sun as her powers continue to further develop.
With that in mind, Kyouko kept an eye with whatever changes that Nezuko may go through.
The same with Akito, since Kyouko theorized that his powers are still developing.
During this time, since Tanjiro broke his sword, Kiyo, Naho, and Sumi told him to go at the Swordsmith Village and ask for Haganezuka.
Kyouko also tasked Akito to go find the village and ask about the Kaedehara Clan's legendary swordsmithin technique, the Isshin Art.
The Isshin Art which is said to be swordsmithing art that is said to be a refine technique that aims harmony between the sword and wielder.
With their respective missions, Akito joined Tanjiro to travel at the Swordsmith Village. A long journey, but it was worth it.
Tanjiro and Akito arrived at the busy village where the nichirin swords are being created.
Akito: So, this is the village, huh. Maybe I can also find some answers about the Isshin Art.
Tanjiro: Isshin Art?
Akito: A swordsmithing technique that is said to be lost in time. The last known practitioner of the Isshin Art was my ancestor, Kaedehara Kazuha, who was said to forge a legendary sword called Kagutsurobe Isshin.
Akito: The sword was said to grant clarity of mind to its wielder.
Tanjiro: Where is the sword now?
Akito: No one knows where the sword is. According to one story, the sword was said to be buried in a secret place.
Akito: A way to bury the secrets of the said sword.
Tanjiro: What about your ancestor?
Akito: My ancestor passed on the Isshin Art to a group of swordsmiths who was said to be the founders of this village.
Akito: In time, the Isshin Art was lost to time, as the swordsmithing techniques that the current generation of swordsmiths, is nothing but an imitation of the ancient swordsmithing technique.
Akito: My mission here, is to learn the lost secrets of the art.
Akito: In order to somehow revive the ancient art.
Tanjiro: I see, I do hope it was passed down properly.
Akito: I do hope so.