Chapter Text
Something in the air gave you nausea. The train’s passengers were all in good spirits, and so was your master, Rengoku, but you were unsettled.
Rengoku noticed. “You must calm yourself! Your nerves are getting the better of you,” his exceptionally loud voice boomed.
“I can’t help but be nervous! Just knowing…” You started to whisper, not wanting anyone to hear your next words, “Just knowing that people have died on this train, it had to have been a demon. What if it’s an upper moon?”
“That's unlikely. And if it happens to be the case," he reassured you, "You have me here. There's nothing the two of us couldn't accomplish together."
You gave him a weary smile, wanting to accept that notion, but it was unrealistic optimism. Even if your bond was unbreakable, your bodies weren't.
Rengoku saw the way you hesitated, the way you failed to fully believe it. He pat your shoulder with enough force to startle you out of your headspace. "You’re not usually in such disarray! Let’s eat. I think a full stomach will do you good.”
“I feel sick, I don’t think I should be eating–”
“Waiter!” he yelled, seemingly not hearing your pleas, “Waiter!”
A young man came by, wearing a crew member’s uniform. He looked tired of Rengoku’s shouting already, but it couldn’t be helped. Nothing could quiet him down.
The employee asked what he needed, and Rengoku ordered that the crew bring him food, and he put a fistful of money in the man’s hand. Just like that, people came by, giving you two box after box of steaming hot food. Your master paid for it, and you weren’t going to waste his money, so you ate – as much as you could, at least. No one could hope to keep up with Kyojuro Rengoku.
The train’s floor rumbled under your feet, and your stomach clenched, telling you it was full. You couldn't let it stop you. You needed to eat more, just like your teacher. It was his philosophy. The more you ate, the stronger you got.
You were slurping down your third box of noodles, willing your stomach to expand to fit more. It was impossible to eat as much as your teacher, but you did notice that you could eat more now than when you first started training.
While you enjoyed your meal quietly, Rengoku let everyone on the train know just how much he liked it by yelling, “Tasty!” after every single bite.
“Excuse me?” a polite voice just barely carried over the hustle and bustle of the train rolling on the tracks.
“Tasty!” Rengoku yelled again.
“Excuse me, Mr. Rengoku?”
You turned your head to see a boy around your age, wearing a green-and-black checkered haori and a Corps uniform. Behind him, a blond slayer and a shirtless kid wearing a boar's head followed. You didn’t have enough time to think about their wild appearances before Rengoku finally acknowledged them.
Rengoku turned to face the boy in green, and you thought he might say something worthwhile, but no. “Tasty!” he shouted right in the boy’s face.
“Yes, I heard you the last ten times,” he said, flashing an awkward smile. He kept calm, but the kid in yellow shied away, startled by the loud exclamation.
Rengoku pointed at the boy in green using the chopsticks in his hand. “You! You were at the mansion.”
“Right,” the boy replied, and his eyes glanced past Rengoku for the first time to land on you. His eyes were dark brown, but they were paradoxically bright and earnest. He swallowed, about to greet you, but he was interrupted.
“Who are these fine young men you have here?” Rengoku said, still as loud as ever, but just as friendly. Rengoku hurriedly finished his food, setting your empty boxes on the seat across the aisle for the crew members to collect later.
“Oh!” the boy said, refocusing. “This is Inosuke Hashibira,” he pointed at the wild boar-man. Then, he gestured to the blond, who wore an orange and yellow haori with a white triangle pattern. “And this is Zenitsu Agatsuma.”
The kid with the boar mask seemed interesting, but definitely unrefined. He snorted out of his nose (the boar’s nose) and grunted out a proud ‘hmph!’ On the other hand, the blond boy seemed timid. He didn’t speak yet, but his eyes were much more adventurous than he was in reality. They darted around the whole room and finally landed on you. You met his gaze for a second before looking at the green boy once again.
You spoke up, “And you, what’s your name?”
“I’m Tanjiro Kamado. It’s nice to meet you! What’s your name?”
You answered, and he smiled, happy to be acquainted.
“They’re my tsuguko,” Rengoku suddenly interjected.
Tanjiro’s mouth opened slightly, and his eyebrows lifted in excitement. “Wow! You’re training under Mr. Rengoku? Are you learning Flame Breathing?”
You sat up, making yourself taller. “Well, sort of. I have my own breathing style derived from Flame Breathing.”
“That’s amazing!” Tanjiro said, leaning in, “What is it?”
“Luminance Breathing,” you replied.
Inosuke butted in, “You must be tough if a Hashira picked you out. I bet I'm stronger, though.”
“...”
“Fight me!” he yelled after the pause. He was socially inept.
“I fight demons, not slayers,” you told him, laughing lightheartedly.
“That's what everyone says. ‘Corps rules’ this; ‘it's taboo’ that. It's sparring. We gotta fight to get stronger.” He must have been hit on the head as a baby. Why else would he be shirtless, wearing a boar’s head, and asking you to spar?
“Maybe when we're not on a mission, okay?”
He was satisfied with that answer. The boys went to sit on the seat across from you and Rengoku. Inosuke sat on the end, Tanjiro in the middle, and Zenitsu by the window – directly in front of you.
You noticed that Tanjiro set down a large box on the floor at his feet, and you couldn’t help but wonder what he could be carrying on his back all day. “What’s that?” you asked, pointing at the seemingly well-crafted box.
He looked down at it with an affectionate smile. “It sounds strange, but my sister, Nezuko, is in there.”
It definitely did sound strange, but Rengoku had told you about a slayer like this. Rengoku had just been at a Hashira meeting for this very thing. A boy carried around his demon sister in a box, and several Corps members vouched for her, even prepared to commit seppuku if she ever came to harm a human. Normally, this kind of thing would never be allowed, but it was a special case.
“This is the demon-girl and slayer-brother duo I told you about,” Rengoku confirmed. He then spoke to Tanjiro, “Since Master Ubuyashiki has accepted her, I will accept her as well.”
“Thank you very much,” Tanjiro sheepishly said, bowing slightly.
“So, why are you all here?” Rengoku asked.
“A crow sent a message,” Tanjiro began, “and we were ordered to join you. The master thought you’d need more manpower.”
The conversation was disrupted when Inosuke started banging on the window on the other side of the train, screaming about being in the ‘belly of the beast.’ You didn’t even notice him walking away – he was unexpectedly sneaky.
Zenitsu leaned forward to look past Tanjiro, yelling at Inosuke, “Sit down! You’re going to break the glass!” He was tense, but he looked like he’d dealt with Inosuke time and time again. You were in for a long night, it seemed.
The train kept chugging, and the yellow boy and the boar were still rowdy. In contrast, you, Tanjiro, and Rengoku mingled in your seats.
“Mr. Rengoku, I was wondering if you knew something about 'fire breathing?'” Tanjiro innocently asked.
“There’s no such thing as fire breathing!” he answered.
“But, my father used to do this dance every year, holding a wooden sword. I think it might have something to do with breathing styles, and it definitely had something to do with fire.” His eyes lit up with the memory of the tradition. “Lately, I find myself replicating the moves of the dance while I’m fighting. You use fire, so I thought maybe–”
“I do not use fire! I use Flame Breathing! I know nothing about this dance, but your using it for fighting is commendable!”
Tanjiro frowned. It felt like he was talking to a brick wall, but he said nothing. “Well, I’m wondering if I could learn something from you, Mr. Rengoku. Anything.”
“Young Kamado,” Rengoku shouted heartily, “You should become my tsuguko!”
“What!?” you yelled, looking between the two of them, your face red with jealousy. You were his tsuguko, not this random boy he just met!
Rengoku calmly told you, “Relax. I can train two young slayers at once. You use light, but Kamado wants flame! It will be good to have someone carry on Flame Breathing.”
Tanjiro looked at you shyly, not wanting to upset you or Rengoku. “Well, thank you, Mr. Rengoku, but–”
Rengoku crossed his arms, excitedly yelling again, “What color is your blade?”
“Black,” Tanjiro answered, embarrassed by it. Black was an unlucky color.
“How unfortunate!” the Flame Hashira roared, keeping his smile all the while. “Hahaha! I hear slayers with black swords have no idea what breath to master! I have not once, in my entire career, seen a Hashira with a black blade!” Way to rub it in.
Tanjiro was disappointed, but not surprised, like he’d heard the same thing a million times. “I’m not going to let that bad luck stop me from protecting people,” he said. He was such a good sport.
You found yourself smiling. His good nature was contagious. “I’m sure you’ll do well, Tanjiro.”
He turned to you and matched your grin, sincerely touched by your faith in him. “Thank you. I’m curious, what color is your nichirin blade?”
“It’s white.”
“I’ve never heard of a white blade,” he said, interested.
“They’re quite rare. I’ve only ever met one other person with a white blade,” you told him, “but it’s not super lucky or anything. It’s just another color, like blue or yellow.” You turned to your teacher, and excitedly boasted about him, “But Rengoku’s sword is bright red! The luckiest color of all.”
“You praise me too much,” Rengoku laughed, but it was full of pride. He wasn’t at all bothered by the admiration of his student.
Tanjiro shook his head. “No, they’re right! Your work is amazing, Mr. Rengoku!”
Again, Inosuke screamed at the top of his lungs, catching your attention, “I’m gonna race this thing! I bet I’m faster!” He was hanging halfway out the window, with Zenitsu holding him inside by the hips.
“I wouldn’t,” Rengoku told him, “A demon could appear any second now.”
“There’s DEMONS on this train!?” Zenitsu yelled, completely forgetting about Inosuke’s bizarre behavior.
“Absolutely!” Rengoku shouted, still grinning with his arms crossed.
Zenitsu came closer, biting his nails between his chattering teeth. “SERIOUSLY!? NOOO!!!”
You curled your lip in disgust, appalled by his cowardice. How did this guy make it past final selection? You answered him, “Well, obviously. Why else would a Kasugai Crow send you here?”
“I thought the train was going to bring us to the demons, but instead, I’m trapped with them!” Zenitsu wailed, falling into a ball on the floor, hugging his knees to his chest and crying.
“Oh my god–” you sighed, looking away from the pathetic display.
Tanjiro winced, mortified by his companion. “Zenitsu, you’re making a scene,” he chided, but his tone was gentle like the summer breeze, even as he reprimanded him.
“I can't help it! We're stuck in a death machine!” the blond whined.
“You're a demon slayer, aren't you? You slay demons! Why are you acting like this is anything new?” you snapped. Why were you stuck with such a crybaby? Just your luck.
“Over 40 people have gone missing,” Rengoku cut in, his voice smoother than butter, “even though we’ve sent in several swordsmen. They, too, vanished. That is why I am here.” He wasn’t nervous at all.
After a short pause, Zenitsu full-on screamed. He rolled around on the floor, shrieking about getting off the train.
Before you could yell at him, the conductor came by. “May I check your tickets, please?” he asked, his voice weak and airy.
Rengoku and the rest of you handed your tickets over calmly, and Zenitsu barely managed to do so through his sobs. “Here,” Zenitsu croaked.
The man seemed strange. He had extremely pale, veiny hands, but he couldn’t have been a day over 30. He must have been horribly ill. You couldn’t imagine that the train company overworked him to the point that he would look like a rotting corpse.
The lights flickered out, and Rengoku blinked slowly, looking more intense than usual. His instincts were usually on point, so you were on guard now, as well.
“Something smells horrible,” said Tanjiro. However, you couldn’t smell anything at all.
“Thank you,” the ticket puncher mumbled once he’d finished punching the tickets, keeping his eyes cast on the floor.
“What smell?” you asked.
Before Tanjiro could respond, Rengoku stood abruptly, making his cape follow behind him in the gust of wind. “Apologies for the sword, conductor, but it has a purpose. Please keep a safe distance.”
The lights continued flickering, going out and turning back on at a faster pace. Zenitsu shook on the ground until he let out a tiny squeal, looking at the other end of the train car. Everyone looked in the same direction, and out of thin air, a large demon appeared. It couldn’t have been shorter than seven feet tall. You and Tanjiro quickly drew your swords, ready for action. Inosuke stood with his fists in front of him, feeling enthusiastic.
“A behemoth has appeared,” Rengoku said, his eyes as wide as saucers, “It was difficult to detect you.” He drew his sword, causing glowing rays of fire to swirl about, and his hair flowed behind him. He was like a knight out of a book. “If you bare your fangs at the innocent, I will turn your bone to ash with my bright red flame blade!” He was so cool!
The demon roared at you all, and its breath reached far. It stank so terribly, and Tanjiro covered his nose with his hand, stitching his eyebrows together in disgust. Zenitsu clung to Inosuke’s arm.
Rengoku looked ahead, putting his sword to his side. You recognized his position – he was about to use the first form of Flame Breathing.
As expected, he jolted forward faster than anyone could even perceive, and after passing the demon, he threw his sword back with a strong chop. It went directly through the demon’s neck, cleanly decapitating him. The head dropped and rolled on the floor to your feet, and Rengoku was braking against the hardwood floor of the next car over. Just as he looked over his shoulder, his red-amber eyes narrowed, and the demon’s body completely exploded midair.
You were freaking out in your head, a little too self-conscious to make a show of your fanfare. Tanjiro, however, had never been privy to Rengoku’s bravado. He whispered, “With only one blow,” with his eyes full of awe.
“Yes! Yes! Isn’t he amazing!?” you whisper-yelled, too excited to keep it all to yourself anymore. You were practically vibrating with energy. Any opportunity to watch your master in action was a gift.
Tanjiro turned to you and nodded. His friends stood behind him silently. Inosuke seemed impressed, even though you couldn’t see his face, and Zenitsu was… still shaking like a leaf. You decided to ignore him and just focus on what was important: the safety of the passengers, and secondly, observing your master.
“There are more,” Rengoku said, “Follow me.” He started running through the aisles, and the passengers all watched as you, Tanjiro, and Inosuke chased after him.
“Hey!” Zenitsu yelled, still in the spot you’d just come from, “D-don’t leave me!”
You clicked your tongue and stopped, staying behind as the other boys ran past you. Zenitsu stood and jogged over to you with a relieved smile, but you were not in the mood to humor him.
“You’re gonna have to keep up. We can’t afford to lollygag. We have hundreds of people to protect on this train,” you told him, wanting him to get it through his head.
His smile faltered, and he pouted. “It’s not my fault that you guys are so fast!”
He had a Corps uniform, so he had to have been good for something. You huffed, “Quit your whining, and let’s go!” You grabbed his sleeve and ran, dragging him along. You let him go once you met with the rest of the group.
A large, arachnid-like demon stood in the middle of a train car. Passengers ran out, back to where you just were, but a few lagged behind. Inosuke jumped toward the demon, drawing two swords. How unusual – they were both serrated, and he was awfully skilled at using them. Maybe he was ambidextrous?
Rengoku lunged forward, tossing Inosuke out of the way and into a seat. “We cannot progress until we get the passengers to safety,” Rengoku told him, grabbing one man and bringing him to the door. Once everyone was out of the car, he resumed, holding his sword in position once again. The demon loomed above him, keeping itself upright with its claws dug into the seats. Rengoku lowered himself and sprang up, severing the demon’s head with the second form of Flame Breathing. The body fell and turned to ash just a second later.
“That…” Tanjiro stumbled over his words, “That was so cool! Please, let me train under you, sir!”
You smiled, so grateful to have someone else recognize your teacher’s prowess. However, it was a little mellowed when Zenitsu and Inosuke shared Tanjiro’s sentiment, giggling merrily about being his students.
“I’ll make you all fine swordsmen!” Rengoku said, happy to take them under his wing.
“Oh brother,” you grumbled to yourself. It was nice and all to have other people to rant to about your master, but you hadn’t anticipated having to share his attention with three other people. Learning would be so much slower now that he wasn’t directly focused on you.
The lights on the train flickered again, flick flick flick, until they went out entirely.