In the next day, Tanjiro and Y/N set off to the forest right in the early morning, both determined to look for Haganekuza.

“I wonder what weapon Kanroji was talking about! Maybe a sword? Maybe it's buried or something! This is exciting! It's like we are on a treasure hunt, right, Y/N?” Tanjiro said, turning to Y/N with a bright smile.

She quickly nodded, sparkles in her eyes : “Right? So exciting!”

Y/N was actually more excited to meet Muichiro, there's no point in getting excited over the 'treasure hunt' when she already knows what the treasure is.

“This is a really great place, but the hot spring smell is strong.” Tanjiro rubbed his nose with a distressed expression. “Hmm… and not being completely healthy is hampering my nose, I can't really smell anything besides hot water now-”

“Is that so? Well, try to see it in a positive light! Isn't it tiring to be able to smell every small thing in a 5-mile radius?” Y/N said, smiling brightly while trying to cheer him up.

“T-that's right, but…”

“But?”

He averted his gaze from her, mumbling with a pout : “But I like your smell though-”

Y/N froze with this statement, hugging herself with a scared expression : “Tanjiro, when did you turn into a pervert?”

“Ah! I didn't mean it like this!” He exasperatedly tried to explain himself, though Y/N was still staring at him in total disbelief.

“I-It's true! I meant that I like it in a comforting way-” Her expression only got worse. “Please stop looking at me like I'm Zenitsu!!”

“Oh! That makes me remember!” Her expression quickly went back to normal. “What do I smell like? I was always curious about this!”

“Huh?” He got momentarily confused at her sudden mood change, but cleaned his throat and responded : “Let me see…. uh- Kinda like apples! Specifically the green ones!”

“Apples...? Wow, that's very- Uh-….unexpected?”

“I like it.” Tanjiro said, his lips curving into a gentle smile.

“Huh?”

“I like it. Apples, I mean.”

'Now talk about a killer smile-' Y/N thought, staring at his smiling face in utter surprise, she had to catch her breath for a second.

“Y/N?” His smile strained after noticing she wasn't responding.

“Ugh- I think I fell in love with you just now-” She jokingly said, dramatically clutching to her shirt like her heart was in pain.

“You! Really-” His face exploded in red for a second, before he looked down with a dejected expression : 'You really shouldn't say these types of things when you don't mean it… it makes me get my hopes high…'

“Hey, Tanjiro, there's someone up there!” Y/N suddenly exclaimed, pointing to a certain location.

Tanjiro followed her gaze. “Hmm? A child? And who's that? Hmm… If I remember that's a hashira, what did Shinobu call him? Oh, right...”

The mist hashira. Tokito Muichiro.

“Get out of here! Whatever happens, I won't give you the key! And I definitely won't tell you how to use it!” The masked kid exclaimed.

'What's wrong? Are they fighting?!' Tanjiro exasperatedly thought. 'what should I do?! Eavesdropping is rude, but if they are fighting, I should probably step in-'

Muichiro silently raised his hand, whacking the kid without any signal of pity, harshly throwing him on the floor.

He then proceeded to grab the child by the collar, lifting him up. “Ughh-”

“STOP! What are you doing?!” Tanjiro didn't waste time and ran up to them. “Let go of him!” he grabbed Muichiro's wrist.

“You're really noisy. Who are you?” Muichiro frowned.

“What are you doing to that child?! Let go of- ugh-” He stared down at hashira's arm. 'I can't budge him! But his arms are thin, and he's smaller than me!'

“YOU let go.” Muichiro glared at him, harshly hitting Tanjiro's stomach with his elbow and effectively throwing him on the floor.

“You're incredibly weak, I'm surprised you got into the demon slayer corps.” He commented, until his gaze fixed in the box on Tanjiro's back.

“Hmm… That box is strange. Do I sense a demon? What's in there? Is that-” He reached out to the box, only to have his hand violently smacked away.

“DON'T touch that.” Tanjiro glared at him so angrily that even Y/N (who was watching the whole thing confused about when she should step him) tremble.

Muichiro silently stared at his throbbing hand, turning to look at his other hand to notice that the kid was gone, and he was only holding his haori now.

“Are you all right?” Tanjiro worriedly asked the kid.

'He got the boy…'

“Hey… lemme go!” He shoved Tanjiro.

“You must be upset, that was close!” The kid smacked Tanjiro's hand away. “Go away!”

The boy harshly stepped away from the burgundy boy, his back hitting against Y/N's legs. “Oh- Hi?” She awkwardly said while looking down at him, she was trying to go up to them discreetly-

“…H-hi?” He responded, until noticing that he's supposed to be angry and shaking his head. “I- I won't give the key to anyone! Even if they torture me! Never! It'll break next time!”

“Have you been trained to withstand torture? Even most adults can't endure it, so it's impossible that you could. You appear to be an exceedingly dumb brat.” Muichiro coldly said. “So what if it does break? Why not make it again? While you're rattling on and on and on with your nonsense, do you know how many people will die?”

'For someone who has amnesia, he really talks a lot, huh?' Y/N thought, boredly looking around while waiting for him to finish his monologue. 'Oh- an ant trail, cool. I will name that red ant Bethany, and that one-'

“That's what it means to interfere with a hashira, your time and a hashira's time have a completely different value. If you used your head just a little, you'd understand. Swordsmith can't fight. They can't save someone's life. They only have the ability to make weapons.”

'That one will be Johnny, that one will be Fiona, and that one-'

“So come on. The key.” Muichiro reached his hand out to the kid. “Know your place in life, and act accordingly. Because you aren't a baby.”

The kid trembled like he was about to cry, but Tanjiro harshly approached Muichiro and smacked his hand away.

“…what are you doing?”

“I….just don't really like this! Why are you acting like this?! The lack of consideration, it's mean and cruel!”

“Cruel? But it was nothing. You-”

“Maybe so! What you're saying is basically true, but- while it isn't technically wrong, the swordsmiths are important and do crucial work! They're different from swordsmen, but they still have incredible skills! I mean, we couldn't do anything if we didn't have actual swords! Right, Y/N?!” He turned to look at her, who jumped from surprise at being mentioned. “Huh?! Yeah, of course! Uh- slay??”

'What are they talking about again???' Y/N got so distracted with the ants that she already forgot what the conversation was about in the first place.

“Swordsman and swordsmiths needs each other! We're both part of the fight! We just each fight in your own places!”

“Sorry, but… I don't have time for this pointless conversation.” Muichiro commented, chopping Tanjiro's neck and immediately making him pass out.

“AAAH- TANJIRO!” Y/N finally stepped in after noticing they finished their monologues, but after seeing the half dead boy on the floor, she kinda regretted interfering now!

But since she's already here, there's no going back, so-

“You- You can't hit him like that! Just because you're cute, that doesn't mean you can get away with these type of things!” Y/N exclaimed.

Muichiro responded by slowly raising his hand.

'Ah! He's going to hit her too!' The kid thought, covering his face intending to not having to see this take place.

You probably won't remember me next we meet, but please be my friend again, okay?

And Muichiro froze, interrupting his own attack attempt.

“How could you hit him so meanly?! Even though it was a really good speech! I didn't hear a big part of it, but-”

Ignoring her rambles, he stared down at his hand with a frown.

“Hey.”

“—And did you really need to make him pass out-”

“I said hey.”

“Uh! Yes?”

“Have we ever met before?”

“Huh? Yeah! At the butterfly mansion! Now that I remember, you forgot this!” She looked around in her pocket before handing a red ribbon to him. “You were using it to know when you needed to remember something! Now where was I again? Oh! Right! What if they were to be seriously hurt-”

Muichiro once again ignored her lecture, silently staring at the ribbon on his hand. Strangely, he felt like he should remember something.

“—And you can't hit people like that! Even more when it's a kid-”

“Y/N.” He suddenly blurted out, interrupting her.

“Huh? HUH? DID YOU JUST SAY MY NAME?! DO YOU REMEMBER ME?!?

“Not really. It just came to mind. Who are you? And why are you even more annoying than your friend on the floor?”

'Oh- so he ended up associating the ribbon with my name after our first meeting? But I guess it doesn't really help if he only remembers the name and not the person-' Y/N thought, tilting her head while staring blankly at him.

“How weird. You annoy me even more than the kid, and you're also wasting my time, but I don't actually feel like hitting you.” He frowned.

“… Thank you?” She confusedly responded.

“Who are you again?”

“I-It's Y/N! You literally said it some seconds ago, how could you have already forgotten it?!”

'A-amazing-' The kid, who was staring at the whole thing in utter surprise, thought. 'It's astonishing how this pair of idiots can't reach to a single line of conversation at all!!'

“…. No matter. I still don't feel like hitting you, so stay right there and don't move.” Muichiro said, ignoring Y/N and walking over to the kid. “The key.”

“Wait! You can't take it from him like that!” Y/N got in between them, honestly speaking, she already knew that Muichiro would wreck her in a second, but if she didn't do anything right now, that kid would probably hate her after.

“I tried to be nice, but you leave me no other choice.” He slowly started to raise his hand.

“W-wait! The key! Here!” The kid interrupted him.

“Huh? Really, you're going to just give it to him after I sacrificed myself?! Now I look way less cool!” Y/N exclaimed, looking over her shoulder to stare at the kid behind her, who exclaimed back with a flustered voice : “I-I'm just trying to help you!! Be grateful that I didn't let you perish by the hand of death!”

“Well, when you put it that way-”

Muichiro's eyebrows twitched in annoyance. Hand of death, really?

With a sigh, he took the key away from the boy's hand, and quickly disappeared.

“Aaaaah- I thought I was going to die!” Y/N let out as soon as he was gone, her legs weakening as she fell down while trembling.

“Were you scared? But you were talking so casually with him-” The kid asked.

“Survival rule, the more scared you are, the more you act like you aren't! In fact, you are already pretty good at that! With the whole 'I won't let anyone have the key even if they torture me!!' thing, it was really good!”

“Is that so? Hahaha-” He meekly scratched his head with a pink aura.“Wait! Don't distract me with compliments!! Who are you?!”

“I'm Y/N!” She politely bowed. “How about you?”

“Oh- I am Kotetsu…” He imitated her.

“Nice to meet you, Kotetsu! I would introduce you to my sleepy friend here, but I feel like it would be better if he does so himself later!” Y/N said, quietly going over to Tanjiro and gently putting his head on her lap, she would feel bad if she left him on the hard floor like that.

“Oh, okay-” He approached the two, crouching down to poke at the unconscious Tanjiro cheek. “Will he be mad at me? He even got hurt to protect me, but I ended up giving the key anyway-”

“Pff, he would never! Don't worry about that! But if that scares you so much, I can take the blame for you! I mean, it kinda was my fault since you gave up on it to help me-”

“No.” Kotetsu shook his head. “Even if you weren't here, I would probably have given it anyway-” He sighed. “Oh! His eyelids are fluttering! He's gonna wake up!”

Just like he said, Tanjiro eyes suddenly shot open. “Good morning sleepyhead! How is your neck feeling?” Y/N said, pointing to her own neck.

Tanjiro stared blankly at her, before slowly raising his hands and starting to pull her cheeks. “Hey! This isn't a dream! It's the real Y/N!”

“Oh- sorry, I just wanted to check-” He said, confusedly getting up. “Where's that hashira?!”

'Now that I think about it, Haganekuza was supposed to appear while he was unconscious, right? I guess he didn't have an opportunity to step out since I am here-' Y/N thought, looking around to see if she could at least catch a glimpse of him.

“I gave him the key, so he left.” Kotetsu responded.

“You gave it to him? It did seem like you had no choice, though.” Tanjiro commented, rubbing his hurting neck. “But I shouldn't really talk, since I don't know what was happening anyway…”

“No, No! I'm happy! You guys don't even know me, but you both stood up for me! Thank you very much.” He bowed.

“But I wasn't any help…” Tanjiro sadly said, flusteredly stopping him from bowing. “But this key, what's it a key to?”

“A mechanical doll.”

“Hmm? Mechanical doll?”

“Yes, my ancestors made it, and it can do 108 movements.”

“Really?! That's amazing!”

“It's stronger than a human, so we use it for combat training…”

“Oh, so he wants to train with it?”

“Yes, but it's getting old and might break…” Kotetsu sadly said, but was interrupted by loud sounds.

“Look like he already started.” Y/N commented, looking at the direction where the sounds were coming from.

“This way!” Kotetsu exclaimed and start to run, while Tanjiro and Y/N quickly followed him.

The three stared in awe at Muichiro and the doll changing extremely rapid blows.

“That's the mechanical doll for combat use that my ancestors made…Yoriichi type zero.”

A mechanical doll that looked like a clone of Yoriichi was in front of them.