Over the past six months, Kochou Shinobu soaked up Nightingale's teachings like a sponge—absorbing every scrap of medical and pharmaceutical knowledge she could.
It wasn't just natural talent—what mattered most was Shinobu's hunger to learn. Before long, she was skilled enough to assist Nightingale in her work.
Of course, the thing Shinobu cared about most was the wisteria poison specifically designed to kill demons.
Besides all that, Shinobu also wanted Nightingale to teach her how to improve her physical strength. Maybe it was because that moment when Nightingale sent Himejima Gyomei flying had shocked her so deeply.
Now that her older sister, Kanae, could no longer fight, Shinobu was determined to take her place on the battlefield. That determination drove her forward.
Kanae had been the Flower Hashira. If Shinobu wanted to fill the gap her sister left, she'd have to become a Hashira herself.
Even if she succeeded in making the wisteria poison, it wouldn't matter if her body wasn't strong enough to inject it into a demon. That's why she wanted Nightingale's help in training.
The problem was—Nightingale was, at her core, just a regular battlefield nurse. What would she know about physical training? All her strength came from [Madness Enhancement EX]. If Shinobu really wanted that kind of power, she might as well become a Berserker herself.
Sure, Nightingale had once trained people while she was Kiichi Hōgen, and even now could probably teach Shinobu to grow stronger… but with her current spiritual foundation, Nightingale had zero interest in anything not related to medicine or disinfection.
So for the most part, it was Kanae who handled Shinobu's training, with Nightingale only offering the occasional bit of advice. After all, even though Kanae could no longer use Breathing Techniques, her experience as a Hashira was still a treasure trove.
Today was the day Kanae would be discharged and return to the Demon Slayer Corps with Shinobu.
Kanae had wanted to go back for ages. She was too soft-hearted, and had adopted several orphaned children, letting them live with her and Shinobu at the Butterfly Estate. As a Hashira, she never lacked money—she could easily provide a life free of worry for so many.
Hashira usually lived at the Corps headquarters, partly for the protection of Ubuyashiki Kagaya. In fact, every Hashira had pleaded at least once to be allowed to leave one or two Pillars to guard the master, but Kagaya always refused.
Power as precious as the Hashira shouldn't be wasted on me. With your strength, you can save so many more lives… That was, more or less, Kagaya's answer.
Since they were leaving, Kanae naturally donned her old uniform—the Demon Slayer Corps uniform and the haori patterned like butterfly wings. Shinobu, meanwhile, only had the plain black uniform.
Looking at the village she'd lived in for over half a year, now surrounded by spring, Kanae was overcome with emotion.
"Thank you all so much for taking care of me… I always wanted to go home, but now that the day is finally here, I can't help feeling a little reluctant… Nightingale, Afune, Tasuke, and everyone who looked after us… If I get the chance, I'll come visit you all again."
"Are you done getting sentimental? If so, let's get moving. There are people waiting for us to save, and if we want to reach the next inn before sunset, we can't afford to dawdle."
Kanae froze, stiffly turning her head to see Nightingale, dressed in that vivid red coat and hauling her enormous travel bag.
"What's with that look—like you're dying to say something but can't decide if you should?"
Nightingale's brow furrowed, red eyes full of impatience. "If you have something to say, spit it out. Don't just stand there like a jammed gun—you're not the only one wasting time here."
"Uh… It's nothing. I just saw you wearing that red coat again for the first time in ages, and it reminded me of when we first met… I was just caught up in the memory. It really does suit you, I think…"
Kanae evaded the question, answering in a roundabout way.
Even though Nightingale had first arrived in this world dressed as Santa Claus, that didn't mean she wore the outfit every day. Over these six months, she'd mostly dressed like the locals—otherwise, the bright red coat stood out too much. Besides, Nightingale always reminded people to "change clothes often and wash your hands." The coat wouldn't get dirty, but if she never changed, people would think, If even you don't follow your own rules, why should we? and her authority would vanish.
If she could maintain her own hygiene, those around her would believe they could too. That was the power of example.
"Seeing you dressed up all of a sudden, I got curious… This is just a casual question, nothing else…"
Kanae bit her lip, and finally voiced the suspicion she'd denied over and over in her mind.
"Don't tell me… Nightingale, are you coming with us to the Demon Slayer Corps?"
"Heh, you're a real comedian."
Nightingale's lips curved slightly, as if Kanae's "joke" had genuinely amused her. "If I'm standing here dressed like this, doesn't that answer your question?"
But in the next moment, the warmth and friendliness vanished from Nightingale's face, replaced by the solemn look of a soldier heading to war.
"I know now. Every member of your Demon Slayer Corps has trained in Breathing Techniques. With so many patients gathered in one place, now that I know, how could I just turn a blind eye? It's far too dangerous to let so many patients without any self-awareness run loose! I've found my battlefield—anything harmful must not be tolerated!"
Her voice rang out, powerful and fervent, making Kanae's heart pound. Her eyes shrank to pinpricks in panic.
Why?!
How did Nightingale know about this?!
She'd been so careful to avoid ever mentioning it in front of Nightingale, just like when she'd had to cover Shinobu's mouth to keep her from blurting it out…
A shock ran through her, and Kanae whipped her head left—only to see Shinobu do the same at that exact instant.
A red vein throbbed on Kanae's forehead.
"You think just looking away will throw me off? Do you think your older sister is that dense?!"
"Ow, ow, ow…!"
Kanae, losing her temper, pinched Shinobu's cheek.
"So you do know pain! It's thanks to your big mouth that half a year of my hard work has gone up in smoke, do you realize that?!"
Kanae could only laugh in disbelief… After learning that Nightingale considered anyone who practiced Breathing Techniques a patient—and might treat them by force—Kanae had gone out of her way to hide the fact that every member of the Corps practiced them.
She was terrified that if Nightingale ever got the wrong idea, she might flatten the entire Corps.
That would make her the greatest traitor in Demon Slayer history—enemies like Muzan would die laughing in their dreams.
And yet… she'd kept the secret well, only to be backstabbed by her own sister.
"What were you thinking?"
Right now, Kanae just wanted to know why.
"What was I thinking? Obviously, I was just jealous!"
Shinobu didn't look the slightest bit guilty, speaking with full confidence. "That medicine is so bitter! Why should I be the only one to suffer? Everyone in the Corps practices Breathing Techniques, so they should get to experience that bracing taste too… Besides, drinking the medicine heals our bodies and fixes old wounds—I'm doing them a favor!"
…
Shinobu claimed she was the only one who'd suffered, but Gyomei had also drunk the medicine. He'd keep coming by from time to time, and Nightingale would always give him more and remind him to take it as prescribed, but Shinobu acted as if Gyomei didn't even exist.
Probably because Gyomei had never so much as flinched at the taste.
"I really don't get what you're so worried about."
While Kanae stood stunned, Shinobu swatted her sister's hand away and spoke breezily, "It's just medicine. Worst case, the ones who are scared of bitterness or won't cooperate might get a mild scolding from sensei—but she's never hit anyone hard enough to actually hurt them."
Her eyes grew a little odd.
"Or are you still worried about sensei's morals or something? Maybe half a year ago we still had doubts, but after all this time, aren't we sure by now? Sensei would never harm anyone in the Corps."
With Shinobu putting it like that, what else could Kanae do?
Even if she managed to win the argument, there was no way she could actually get Nightingale to change her mind. Trying to stop Nightingale from saving people was about as realistic as hoping a demon might go vegetarian—if anything, the latter might actually be easier.
"Nee-chan Shinobu and Nee-chan Kanae always get along so well. Watching you two is so much fun—I'm really jealous! It's such a pure, sisterly bond, right, Tasuke?"
"Ya ya!"
"Tasuke's excited too! Me as well—after all, it's my first time leaving the village for somewhere so far away. On the road, Tasuke, you have to be good, okay? Don't cause trouble for Nightingale-oneesan or the others."
"Ee-ya!"
Afune, standing obediently by Nightingale's side, caught Kanae's attention, distracting her from punishing her traitorous sister.
"Afune's coming too? And carrying Tasuke on her back…"
Kanae looked at the two, then turned a worried glance toward Nightingale, who held the highest authority in the group. "Can such young kids handle a long journey? They've never left the village before, have they?"
"I'll take care of them."
Nightingale's expression didn't change as she answered calmly, "Honestly, they're better off with me than staying in the village… Besides, you're underestimating them. They're tougher than you think."
"Is that so? Well, if you say so…"
They didn't have much luggage, setting off light and fast.
The Corps had supply points scattered all over Japan, so there was no need to bring much besides a bit of grain in case they got hungry before reaching the next stop.
Even if they had brought a lot, it wouldn't matter—Nightingale's travel bag worked like a four-dimensional pouch: it could hold almost anything. The only catch was it couldn't shrink items, so anything larger than the bag's mouth wouldn't fit. She couldn't, say, pull a door out of it like a certain blue robot cat.
…
The moon was high and the stars faint. In the silent forest, even a bird's call might startle a person.
Whoosh—
The wind howled.
A demon, skin twisted in a grotesque blue-green, tore through the wilds. Muscles bulged along his legs as he ran, so fast it seemed he left the very wind behind.
But despite that, his face was twisted in frustration.
Damn it… I thought I'd gotten lucky tonight—so many young, pretty girls at once, but it turns out there were Demon Slayers mixed in…
He dared not slow down, pushing his speed higher and higher.
That scrawny brat looked weak, but she kept pace with me the whole way… What the hell—could she be a Hashira? Good thing she's not very strong—couldn't quite cut off my head… Hmph! I've memorized that face. Once I eat a few more humans and earn the Master's favor, I'll become one of the Twelve Kizuki. Then I'll hunt them all down and devour them!
Hate twisted his already monstrous face.
The demon was confident in his speed—his Blood Demon Art was all about running faster than anyone. He'd eaten more than one Demon Slayer this way. But tonight, it hadn't been enough, and for the first time, a girl kept up with him. He was sure she must be a Hashira.
Curious, he looked back to see if the suspected Hashira was chasing him and how far behind she was.
And in that instant, the demon nearly died of fright.
A beautiful, delicate face entered his view—but her eyes were icy cold, radiating nothing but murderous intent.
The next moment, a modified Nichirin Blade shot forward, a flash of cold steel bursting like lightning. Before the demon could react, the blade had already pierced through his neck.