It was a new day and they were training again. Tanjiro nearly managed to win but Kanao got to the cup first.

Tanjiro: You really are fast, Kanao

Kanao said nothing.

Izuku: The score is now 10-10.

Tanjiro: I'm still up for more. Let's go for a run. Zenitsu, Inosuke, wanna join?

Zenitsu: Doing total concentration, constant?

Izuku: Yeah.

Tanjiro then smacked Zenitsu in the stomach.

Zenitsu: I gotta keep this up.

Inosuke: DO ME NEXT!

Zenitsu started to punch Inosuke.

Zenitsu: How's this?

Inosuke: That's nothin'!

Zenitsu: More brawn than brain.

Tanjiro: Let's go.

(The next morning)

Kusagai Crow: It is now morning!

Inosuke: The hell?

Zenitsu: What's going on?

Kasugai: The casualties of the Mugen train. More than 40 are missing as it currently stands. You four are to join Kyojuro Rengoku on-site. Head west at once! Head west at once!

Izuku: Awesome! My first mission as a Demon Slayer!

Nezuko: And it's my first time going on a mission as a human! Wait. Who will take care of Eri? No way are we bringing her along!

Eri: Don't worry mommy. Ms. Kanao will take care of me.

Nezuko: Oh. That's good. I trust her.

(Later)

Ubuyashiki: For the Mugen train mission, I have decided to send Tanjiro and the others. This will be Izuku's first mission as a Demon Slayer. Might I ask what caused you to recommend them in the first place, Shinobu?

Shinobu: Tanjiro and Izuku both have pure souls and will work diligently toward all their goals, and the potential they showed exceeded my expectations. And perhaps most importantly of all, they have a clear path in mind in regards to defeating Kibutsuji.

Ubuyashiki: I am in complete agreement with you on those counts.

Shinobu: On another matter,  Tanjiro told me that his father had used Fire Breathing.
Ubuyashiki: Ah.

Shinobu: As of now, there is no denying that the two still have quite a way to go, but I think that Rengoku, our Flame Hashira, could give them assistance.

Ubuyashiki: Fair enough. Considering that his sister is not ever going to be a danger to humans thanks to Eri, as well as the fact that Tanjiro came face to face with Muzan, these signs may very well point towards this being Tanjiro's destiny.

(Later)

Aoi: Good luck out there you two. Take care now.
Tanjiro: Thanks for everything.

Izuku: We appreciate you looking after us, even though you were busy yourself.

Tanjiro: And now we can get back into battle.

Aoi: No need to thank me. It was by chance I got through Final Selection, and after that, I was too cowardly to even step foot in battle.

Izuku: So? You still helped us out, Aoi. Not all heroes fight villains. Sometimes, a hero needs a support hero. I can't tell you how many times I had to be healed by Recovery Girl.

Aoi: Recovery Girl?

Izuku: She's a hero. But her quirk isn't for fighting villains. Instead, it speeds up the healing process. While she can't really fight against villains, she is a great hero who still helps out. That's what we call a Support Hero. In my opinion, you're a Support Hero. You helped us not in battle, but in health.

Aoi: Izuku...thanks...that's really nice to hear.

Izuku: If we get hurt again, well, we trust you to look after us again. Bye.

And with that, Izuku and Tanjiro left. They then found Kanao.

Tanjiro: There you are!

Izuku: Hey Kanao! We're heading out now. Thanks for everything.

Kanao just smiled.

Tanjiro and Izuku: Uh...

She then brought out a coin.

Tanjiro: Hmm? What's that?

Izuku: That's a coin.

She then flipped it and when she saw what it landed on, she spoke.

Kanao: All I did was follow the teacher's orders, and so there's no need for you to thank me. Farewell.

Tanjiro: 'She actually talked to me!'

Tanjiro: Why did you flip that coin?

Izuku: Come to think of it, I saw you do that the same day we met.

Kanao: Bye for now.

Tanjiro: You sure made that thing spin.

Kanao: I flip this to help me decide things that weren't ordered. Just now, I decided whether to speak to you or not. Don't speak was heads, and Do speak was tails, and tails is what it landed on. Farewell.

Izuku: 'That doesn't seem like a good idea.'

Tanjiro: Why don't you choose for yourself? Which do you wanna do?

Kanao: It doesn't matter.Nothing matters to me, so I can't decide for myself.

Tanjiro: I don't think there's anything in this world that doesn't matter. I guess...the voice in your heart is just really tiny. Hmm...following orders is important to an extent, but...hey, can I borrow that?

Kanao: Sure.

She gives the coin to Tanjiro.

Tanjiro: Thank you. Okay, we're gonna use this to decide!

Kanao: Decide?

Izuku: Decide what?

Tanjiro: Whether you'll listen to your own heart from this point on!

He flips the coin. Really high.

Tanjiro: Woah! I flipped it way too high! Heads! Let's make it heads! If it comes up as heads, you're going to follow your own heart, Kanao!

Then a gust of wind blew and the coin disappeared.

Tanjiro: Where did it go?

He then found it and caught it.

Tanjiro: You see that, you two? I got it! Are you ready?

Izuku: Let's see it.

Kanao: 'Which will it be? His back was blocking it, so I couldn't see which way it fell.'

It was heads.

Tanjiro and Izuku: It came up as heads!

Tanjiro: Here you go!

He gives back the coin. And then grabs Kanao's hands.

Tanjiro: Remember! It's the heart that drives people, so it cangrow as strong as you need it to.

Izuku: All right. See you later!

Izuku and Tanjiro took off but,

Kanao: How-How did it come up heads?!

Tanjiro looked back. Izuku did too.

Kanaoo: 'I saw his hand when he flipped it. I'm sure he didn't cheat but still...'

Tanjiro: Just by chance. Although, if it were tails, I was gonna keep tossing it until it finally came up as heads.

Tanjiro: Take care of yourself!

Izuku: Bye!

(Later)

Tanjiro, Zenitsu, Inosuke, and Izuku all blew into the giant gourd and eventually, they all broke it.
The girls gave them some rice balls and Zenitsu and Inosuke were fighting about eating them right this moment.

Tanjiro: Tomioka!

Tomioka: Heading into battle now?

Tanjiro: Yes sir.

Tomioka: I hear that you've mastered total concentration, constant.

Tanjiro: I have.

Tomioka: You should keep at it.

Tanjiro: Yes sir. Also, about Nezuko...thank you very much. The fact that you put your life on the line, I had no idea. I don't know how to ever repay you.

Tomioka: You can thank me by doing your best work. Our mission is to kill demons. That is all. Got it?

He then leaves.

Tanjiro: Got it!

Izuku: Are you Ok Nezuko?

Nezuko: Yeah. Just a little nervous.

Izuku: You'll do great! Don't worry.

Nezuko kisses his cheek.

Nezuko: Thank you, Izu.

Izuku blushes a little.

Izuku: Y-You're welcome!

Tanjiro: All right everyone! We're heading out now!

And so they left for the train station.

Inosuke: Hey, wait a damn minute! Wh-What the...WHAT THE HELL IS THIS CREATURE?! Wait. Could it be? I've heard of such a being. The master and ruler of this land! At such an intimidating size, there's no mistaking it! It looks like it's asleep, but don't let that fool you!

Zenitsu: It's a train. You've never seen one?

Inosuke: Pipe down, or you'll wake it!

Izuku 'Didn't you just say it was only faking it?'
Inosuke: I'll lead the charge to take it down!
Nezuko and Tanjiro: Inosuke, stop!

Inosuke: Huh?

Tanjiro and Nezuko: This might be the guardian spirit of this land, so we shouldn't be attacking it carelessly.

Izuku: Actually, it's a mode of transportation. This is what the Kasugai crow was talking about. This is a train.

Nezuko: Oops. I feel silly now.

Inosuke backed away. And then...he headbutted it.

Inosuke: Ready or not, I'm coming through!

Zenitsu: STOP EMBARRASSING US!

Conductor: Hey! What do you think you're doing?

Izuku: Uh oh.

Conductor: Look! These four have swords! Call the police!

Zenitsu: NOT GOOD! NOT GOOD! NOT GOOD! RUN FOR IT!

Zenitsu drags the other 4 away as fast as he could.

Zenitsu: We went through HELL  'cause of you, Inosuke! Say you're sorry!

Inosuke: Oh yeah?! Explain to me why we had to run from those guys in the first place?!

Izuku: 'Cause Demon Slayers aren't officially recognized by the government, so we can't just have our swords out in public like that. If we told them about the demons, I doubt they would believe us, anyway.

Tanjiro: But we're trying hard to help everyone.

Izuku: I'm afraid that like my homeroom teacher, Mr. Aizawa says, the world is full of unfairness. It's just our job to combat that unfairness. But for now, we should hide our swords.
Inosuke laughs and puts them in his pants.

Zenitsu: We can see them. Put something on.

Izuku: Guys. The train's leaving.

Everyone: WHAT?!

Inosuke: HERE I COME, MASTER OF THE LAND!

Zenitsu: What are you doing?!

Izuku wraps up Zenitsu, Tanjiro, and Nezuko in Blackwhip and activates One for All at 30%

Izuku: Hang on!

Izuku then brings them up to the caboose of the train. Inosuke followed quickly after. However...

(Inside the train)

Rengoku: Are you ready for this mission?

???: Hell yeah.

(Who could that be?)