"How effective is the drug that accelerates a demon's cellular aging?"
"Not bad... but it's only truly effective on ordinary demons. It's unrealistic to expect it to work just as well on the progenitor—Kibutsuji Muzan."
Nightingale's words made Tamayo frown; it was clear that answer didn't satisfy her.
"So we still need that medicine that can turn demons back into humans? To defeat Muzan, we'd have to inject both drugs into him at once?"
"The problem is, the demon-to-human drug is incredibly complicated."
Nightingale spoke with her usual calm. "We'd need to return to Demon Slayer Corps headquarters and use their resources to speed things up. If we did that, based on our estimates, we could finish the demon-to-human drug in about ten years."
At this, Yushirou broke in, agitated.
"You want me and Tamayo-sama to go to the Corps—full of demon slayers? Are you out of your mind?!"
Even if their goals were aligned, Tamayo and Yushirou were still demons—Tamayo was once a man-eating demon herself. Yushirou didn't trust the Corps to be at all welcoming.
"Yushirou."
Tamayo's low, firm tone made him tense up reflexively, but he still wasn't willing to give in. He clenched his teeth, looking at Tamayo.
"Tamayo-sama!"
"It's all right, Yushirou. We agreed to this from the beginning."
Tamayo shook her head, her voice grave. "Our chance to kill Kibutsuji Muzan is right in front of us. I can't let it go. Besides, the Ubuyashiki clan head promised us in advance: if we go to the Corps and help them against Muzan, he'll keep his subordinates in line and guarantee our safety."
Seeing Tamayo's resolve, Yushirou could only glare resentfully, but he didn't argue further.
Though Nightingale suddenly received a venomous glare from Yushirou, she could only sigh inwardly.
It was Tamayo's own decision—not like I put a gun to her head. Why glare at me?
"If that's settled, then let's get moving today," Nightingale said, pushing off from the table with a certain urgency in her tone. "There's no time to waste—let's pack up what we need before nightfall. My travel bag can hold plenty."
Tamayo watched Nightingale's back, visibly wrestling with herself, then spoke slowly.
"Please wait, Miss Nightingale. There's something I absolutely must ask."
Seeing Nightingale pause and turn, Tamayo organized her thoughts for a few seconds before finally speaking.
"The last Blue Spider Lily in this world... is it in your hands?"
A heavy hush descended; even the air seemed to freeze.
After a long silence, Nightingale took out a flower.
It looked like a spider lily, but instead of red, its petals were an uncanny blue.
The moment it appeared, both Yushirou and Tamayo unconsciously held their breath—their eyes glazed, unable to look away from the flower.
In a trance, Tamayo's voice trembled with emotion as she finally managed to speak.
"That's... the Blue Spider Lily..."
Her tone was filled only with awe, not doubt—her very blood seemed to burn inside her, screaming that eating this flower would grant perfect immortality.
Tamayo forced herself, with an iron will, not to drool. She shifted her gaze from the flower to Nightingale's face, despite her dry mouth.
"It's certain—this is the Blue Spider Lily Muzan has searched for all these years..."
As she said Muzan's name, the gentle warmth in Tamayo's smile vanished, replaced by hate. "The Blue Spider Lily that would let Muzan overcome the sun. He's searched for it for a thousand years, but we found it first. I'd love to see his face when he hears that..."
Once Tamayo regained her composure, she grew serious and asked, "Is this really the last Blue Spider Lily in existence?"
Nightingale met her gaze and nodded solemnly.
"I'm the only person left who knows where the Blue Spider Lily is. Not long ago, I destroyed nearly all of them—this one is the last."
"But you didn't destroy the last one. Why?"
Tamayo's eyes narrowed, locking onto Nightingale's. "If you got rid of it, Muzan would never become a perfect immortal."
"And no one knows what Muzan would do then."
Nightingale frowned slightly. "You know what he's like. Muzan spent a thousand years chasing this flower. If he ever finds out every last Blue Spider Lily is gone—that his last hope is truly lost—he might go completely mad. He could launch all his demons in a reckless final assault on humanity, burning the world to the ground."
Tamayo said nothing; with her understanding of Muzan, she knew Nightingale was right.
He'd hidden for centuries after being wounded, waiting until his enemies died of old age before emerging. You couldn't expect any decency or restraint from someone like that.
His obsession with survival trumped everything—he was the kind of monster who would trample anything good for just one more day alive.
"At the same time, this last Blue Spider Lily is an insurance policy."
Nightingale's words caught Tamayo's attention.
"Muzan is a master of hiding. Trying to find him among the masses is like searching for a needle in a haystack. Our real fear is that he'll do exactly what he did in the Sengoku era: vanish for another hundred years, waiting us out. That's why I kept this last flower—so we can force him into the open."
"He's waited a thousand years for this. When hope is finally in sight, he won't be able to resist. We can tell him it's the last one—if he refuses to come, we'll destroy it. That way, he'll have no choice but to walk right into our trap."
Nightingale didn't need to elaborate on what "trap" meant. Tamayo could imagine it: the specialized anti-Muzan drugs, and the combined force of Nightingale and the Hashira.
"So, as soon as the medicine is ready, we can move forward with the plan?"
"It'll take at least ten years."
Nightingale's tone was calm. "You can wait that long, can't you?"
"Of course."
Tamayo's lips curved in a faint, satisfied smile. The chance for revenge was almost in her grasp. "I've waited centuries to kill Muzan. What's ten more years?"
Their conversation, in the empty ramen shop, would never reach a fourth person.
...Or so it should have been.
In fact, an eyeball had been watching through a hole in the wall ever since Nightingale arrived.
It stayed until the conversation was over and the three left, then, as if chased by something terrifying, the eyeball scuttled away on thin tendrils.
Through chilly, narrow alleys, Nightingale and the others made their way back to the main street.
Though the sun had nearly set, colorful lights flickered everywhere. In a village, people would already be asleep at this hour, but Asakusa was only just getting livelier.
With progress and modernity, the age of the night owl had begun.
Of the three, Nightingale trailed behind, constantly turning her head—gawking at the city's bustle like a country bumpkin.
Only when she felt that prying gaze finally vanish did she whisper to Tamayo, "All right, we can talk normally now."
"Muzan's spy has left?"
Tamayo's hand, hidden in her sleeve, was clenched so tightly her palm was slick with sweat.
"Did we give ourselves away?"
"No. Your acting was perfect, don't worry. Muzan won't suspect a thing."
Seeing Tamayo's unease, Nightingale reassured her. "Besides, most of what you said was true—I handled the lies."
Tamayo exhaled and managed a hopeful smile.
"If Muzan believes everything we just said... he's as good as dead."
The Blue Spider Lily has reappeared; Muzan's thousand-year obsession is finally within reach.
But for Tamayo, her wish was just as strong: to kill Muzan, to drag him down into hell alongside herself. And until she met Nightingale, she'd never seen a true dawn for that wish.
...
In the cheerful courtyard of the Butterfly Estate, the innocent laughter of children seemed to make the sun shine even brighter.
Here lived the retired Flower Hashira, Kochou Kanae, and the newly promoted Insect Hashira, Kochou Shinobu.
Most of the Demon Slayer Corps knew that this new Insect Hashira was skilled in medicine and pharmacology. The Butterfly Estate had gradually become the Corps' main medical center—providing treatment and rehab for the sick and wounded.
Shinobu's plan for today was a sunbath and some freshly made osmanthus cake—until she couldn't stand the burning gaze aimed her way.
"Neesan! Why do you keep staring at me like that?"
Shinobu, still holding her half-eaten cake, shot a look of protest at Kanae.
"And just so you know, all this cake is mine. If you want any, go make your own in the kitchen!"
"Why should I? It's not like you made it yourself—didn't you have Kanao make it for you?"
Kanae was unimpressed by her sister's shamelessness.
"But that's not what I'm worried about..." Kanae said, watching her sister eat with bliss.
"Have you... gained weight?"
Shinobu's happy munching froze, her expression turning horrified.
"E-even if you're my sister, I won't let you say something so irresponsible! That's totally slander!"
Shinobu sprang to her feet, face red as a cherry, finger shaking as she pointed at Kanae.
Kanae just rolled her eyes. "Serves you right. Everyone else is training hard for the upcoming battle against Muzan, but you're lazing around. No wonder you're putting on weight. You became a Hashira the same year as Muichirou, yet he's way more motivated than you."
"That's not fair, neesan!"
Shinobu collapsed onto the table, grumbling. "I want to join the others' training, but all they do is spar, and my fighting style's so different I can't join in. If I try, my wrists can't even hold up a sword!"
"And don't compare me to Muichirou—that kid's a monster... Who'd have thought anyone could become a Hashira, and slay a Lower Moon, in just three months?"
Mist Hashira Tokitou Muichirou was a prodigy who rose to the top in only three months.
Unlike the original story, his brother hadn't been killed by a demon, and he hadn't lost his memory. When both brothers were attacked, Nightingale happened to be there and saved them both.
Afterward, just like in canon, Muichirou chose to join the Demon Slayer Corps. In fact, the Ubuyashiki family had tried more than once to recruit the Tokitou brothers, knowing they were descendants of the original Breath Styles.
It was only after the demon attack that the brothers reconciled, and Yuichirou no longer stopped Muichirou from helping others.