Koshinobu ran through the woods, fighting off demons and looking for places to rest, he eventually heard a boy screaming for help as he was cornered by a giant demon with hands surrounding his neck. He went to fight off the demon as the boy ran away, Koshinobu attacked the demon but failed a few times but managed to defeat the demon and continue to defeat the demons remaining in the forest for 7 days.
-7 Days Later-
Koshinobu arrived back to when he first arrived in the Final Selection, 3 people managed to survive the Final Selection, the boy he saved back then didn't survive. The two women congratulated them and told them the ranks of the Demon Slayer Corps, Mizunoto, Mizunoe, Kanoto, Kanoe, Tsuchinoto, Tsuchinoe, Hinoto, Hinoe, Kinoto and Kinoe. They also told them that they could pick which ore they'd like for their nichirin, there was this one person who was complaining and grabbed the young girl doing absolutely nothing as Koshinobu grabbed the boy's arm and squeezed it telling him to let go of the girl and so he did. The four remaining Demon Slayers picked out their ore and left back to their homes.
-Night-
-Osorochi's Home-
Koshinobu: SUSA-SAN, OSOROCHI-SENSEI!!
Susamaru: -immediately comes out of the house and hugs Koshinobu- Congrats on being a Demon Slayer!
Osorochi: -hugs Koshinobu as well- I'm so proud of you Koshinobu.
Koshinobu: Thanks, Osorochi-Sensei.
Osorochi prepared another feast for Koshinobu as Susamaru played with her temari ball.
Osorochi: So you managed to survive the Selection, most people don't survive unless their lucky, you're one of them. -gives a bowl of Udon to Koshinobu-
Koshinobu: Thank you, Osorochi-Sensei. -eats the bowl of Udon-
Osorochi: You've been assigned with a Kasugai Crow, correct?
Koshinobu: -mouth full of Udon- MHM, YEAH THEY GAVE ME A CR-
Osorochi: -slams my fist on his head- SHOW SOME MANNERS, BOY!
Koshinobu: -swallows my food- SORRY, OSOROCHI-SENSEI!
Osorochi: Hm...these crows give out missions so remember that.
Koshinobu: Understood.
Osorochi: As you step out of this house remember this. There are demons who have no powers but there's more that have specific powers, they are called Blood Art Demons and they are dangerous, even to a boy like you. So be on alert and also I should tell you one more thing...there is one demon who seeks to live during the daylight, someone who's the most powerful demon that we've ever faced..his name is Muzan Kibutsuji.
Susamaru immediately backed away in fear as she heard his name being mentioned.
Koshinobu: Susa-San, you okay?
Susamaru: that name....that name isn't supposed to be spoken of by demons.
Osorochi: -looking at Susamaru while eating-
Koshinobu: How come?
Susamaru: I'd rather not say...but if I say his name or even mention it...I don't think I'll live much longer.
Koshinobu: Well, I'll make sure you don't and that's a promise!
Susamaru: Thank you.
Osorochi: Hm...well get some rest, because tomorrow you guys will be on a journey not even I can help you in.
Koshinobu: Right. -heads to bed with Susamaru-
-The Next Day-
Koshinobu looks around outside as a man with a woven hat that has wind chimes walks to Osorochi's home.
??: Are you Koshinobu Kamado?
Koshinobu: Uh, yeah that's me!
Osorochi: Looks like you took your time, Hotaru.
Hotaru: As always, anyways let's get this over with.
Hotaru enters Osorochi's home along with Osorochi and Koshinobu as they enter.
Hotaru: -hands over Koshinobu's nichirin with the same half-holes like the nichirin he used for Final Selection- Now let's see that nichirin color.
Koshinobu grabbed the nichirin blade and held it up as the color quickly changed to a black color.
Osorochi: Hm, that's odd.
Hotaru: A BLACK COLOR ARE YOU CRAZY!! -grabs Koshinobu- I EXPECTED MORE FROM THAT!
Koshinobu: WHAT DID I DO WRONG!!!?
Hotaru finishes getting mad at Koshinobu as he leaves Osorochi's home.
Koshinobu: What does this mean when my nichirin blade is black?
Osorochi: -sighs- not much is known about it but it means that the wielder might not make it for too long.
Koshinobu: Oh...-looks at the nichirin- well I can't back down now...-gets up and changes to my Demon Slayer Corp outfit-
Osorochi: Koshinobu, I made you a box for Susamaru so that she can stay in during daylight.
Koshinobu: Ah, thank you, Osorochi-Sensei!
Koshinobu grabbed the box and went inside the room Susamaru was sleeping in.
Koshinobu: Susa-San, I don't know if you can fit in here but at least try so we can still be together.
Susamaru: -shrinks and gets inside the box-
Koshinobu: ALL RIGHT, I'll get you out the box as soon as the moon comes out, I promise!
Susamaru: -nods and sleeps as Koshinobu closes the box-
Koshinobu walked outside after getting his gear ready, he waved bye to Osorochi, starting his new journey as a Demon Slayer.
-DEMON SLAYER: OCHIRU TSUKI(FALLING MOON)-
After being called by Koshinobu's crow about a mission, he made it to the town where the mission was being held.
Koshinobu: Alright, I made it...now I just gotta look around.
Just when Koshinobu said that a random man was thrown out of a house, bruised by another man who was shouting at him alerting anybody around him. Koshinobu runs to the man and helps him up.
Koshinobu: Hey, are you alright?
Man: -gets up wiping my tears- Y-Yeah I'm fine.
Koshinobu: What's the matter, why was that man hurting you?!
Man: Let me explain.
As the man explains the story how his fiancé disappeared during the night while walking through town with her Koshinobu immediately knew this could be the work of a demon.
Koshinobu: That could be related to a mission I'm doing, where was the last place you saw her!
Man: Um, uh right there..why-
Koshinobu: -points to my nose- I have a strong sense of smell so I'll be able to smell the demon, FOLLOW ME! -follows for the demon's scent-
Man: -in mind: Jeez what's with this guy?-
The man followed Koshinobu as they begun to look for the lost woman and finish off the demon.
-That Night-
Koshinobu and the man were still searching which lead them nowhere to the man as he gave up.
Man: Let's just give up, we can't find her it's useless.
Koshinobu: W-We have to keep trying I know the demon has to be here, I sense it's scent so your fiancé should be found in no-
Just then the man punched Koshinobu to the ground as blood cane out of Koshinobu's nose.
Man: -grabs Koshinobu- CUT THE DEMON BULLSHIT THERE'S NO SUCH THING AS A DEMON, JUST FORGET ABOUT I-
Suddenly Susamaru's box opened, as she stepped out of her box, staring at the man.
Man: -lets go of Koshinobu and backs away- S-Stay back....please.
Susamaru: -rubs my robe under Koshinobu's nose, cleaning the blood off- You okay, Koshinobu?
Koshinobu: Yeah I'm fine, thanks Susa-San.
Susamaru: Yeah, hey you!
The man backed away even more as Susamaru approached him.
Man: PLEASE I DIDN'T MEAN TO IM SOR-
Susamaru: -puts my hand on his head- It's okay you were just angry and frustrated about your fiancé...but right now we need to find her and defeat this demon because we're going to run out of time-
Koshinobu: GUYS, I SMELL THE DEMON...AND THE SMELL OF A GIRL!
Man: -jolts up- THAT MUST BE HER!
Koshinobu: Only one way to find out, SUSA-SAN, HAVE MY BACK ALRIGHT!
Susamaru: On it! -gets behind Koshinobu's back-
Koshinobu and Susamaru look around for the demon as a swamp puddle appears in front of Koshinobu as he sees a girl being carried by a demon.
Koshinobu: I SEE HIM!! -runs to the demon- CLOUD BREATHING FIRST STYLE: ROLLING CLOUDS!!
Koshinobu gets close to the demon and raises his nichirin blade from below, almost cutting the demon's hand off as he let's go of the woman and returns into the swamp puddle as it closes.
Koshinobu: Damn, I was too late...-walks to the woman and checks her pulse- She's still alive, just unconscious. -grabs the woman and walks to the man- Is this your fiancé?
Man: No that's not her, she has a pink ribbon on the back of her head.
Koshinobu: So this isn't her...I'm guessing the demon still has her-
Just then three swap puddles formed around them as the demons came out shredding their teeth.
Koshinobu: -hands the woman to the man- Take her and stay with us, don't move away from here!
Man: G-Got it!
Swamp Demon: Hm...So a Human and a Demon working together, that's the oddest thing I've ever seen in my life1
Swamp Demon #2: GRRR, I DONT CARE ABOUT THAT I JUST WANT THAT GIRL, SHE'LL TASTE SO SWEET THAT I CAN'T RESIST IT!
Swamp Demon #3: ...
Swamp Demon: Hand over the girl, now. DONT YOU SEE THAT WE CAN'T SURVIVE WITHOUT TASTING THE SWEETNESS OF A YOUNG WOMAN!
Koshinobu: Like hell I'm going to give her to you!
Swamp Demon: Have it you're way..-almost makes it down the puddle but gets a temari ball thrown at my face- GAH, WHAT THE HELL!?
Susamaru: Hey Koshinobu, I'll guard them both from here, you focus on getting one of them.
Koshinobu: Right. -runs to one of them and has by nichirin below again- CLOUD BREATHING FIRST STYLE: ROLLING CLOUDS!
-To Be Continued in Ryoichi Chikasei, Lava Mizunoto-
