It's not just a "Nen beast." More precisely, it's a Conjuration-type Nen beast.
Roy swept his gaze over the old woman and the "children" behind her. Like Kite's ability "Crazy Slots," they had physical substance—ordinary people could touch and perceive them… which is exactly why Kuraging, who hadn't opened her nodes yet, could see them.
Same reason Gon, Leorio, and Kuraging could see them in the original story.
Aboard the Association Airship, Zeno finally dragged his eyes off Kuraging and onto the ring of "child-beasts." He cut Netero a sidelong look—apparently the Association had a hidden figure like this…
A single person maintaining a stable of Nen beasts—this old woman looked about his age, but her "nen reserves" were anything but ordinary.
"Ho-ho-ho… no need to be shocked." Netero popped the last bite of cake and sipped the tea Mamen Beans handed him. "Sachiko's not a combatant. She wants to keep them—old me can't talk her out of it."
"Wantonly spending aura shortens one's life—that's common sense."
"She's not common. Bean, tell him."
"Understood."
Mamen Beans—world's oldest "kid"—poured Zeno a cup and explained with care: "Nakajima Sachiko is the old woman blocking your grandson…."
Pfah. Calling her "old"—Mamen Beans was far older. By age, it was the biggest antique in the room. It tamped down the odd feeling and continued: the Orphanage Dean of Yorknew City, survivor of a fire that took every child. In that shock, her Nen awakened—Heaven's Dolls—call forth aura and Conjure dolls to fight. But she chose otherwise.
Before the orphanage ruins she swore: no fighting, never raise a hand—an oath traded for true imagining. She poured her soul into recreating the dead children, Conjured them into "Nen beasts," and housed them in dolls. Thus, the "children" on-screen.
"Nen" reflects the truest mind. When the Chairman learned of her, he honored her love, secured a sanctuary for her and those children—this little town.
"A pity… with her reserves she could've been a fine fighter." Zeno set down his cup, thinking of Milluki; by Luke's reports the boy was useless—lazy with no talent. Even if he nudged him down the assassin's road, it'd be a slog…
Netero's sidelong glance sharpened. "Not everyone's a Zoldyck—fond of killing and combat."
He slouched into the sofa, memories drifting. "At the Association, we respect each Hunter's Dream. If Sachiko loves being with the kids, even if she won't fight—so be it."
"Old me isn't short one more fighter…"
Zeno nodded. "If Beyond were here and heard that, he'd weep…"
"Shut it!" Netero snapped and pitched a teacup. Zeno caught it, smiling. Big speeches aside, the Chairman still couldn't handle his boy. Zeno ignored the murderous side-eye and returned to the screen…
Nakajima Sachiko planted her cane and pulled a fearsome face. "Riddle—riddle—two-choice heartbeat quiz!"
The shout jolted Kuraging; she clutched Roy's arm tighter.
"Crack—" Gotoh laced fingers into a fist—the joints popped like frying beans. He cut Kuraging a sideways look like she was already dead.
Roy didn't move. His eyes traced from Sachiko to the children, unreadable.
Sachiko watched him warily and said, "Next, I'll ask a question. You have five seconds. One mistake—you're out."
She was a proctor too. The red bead on her cane caught Kuraging's eye—it bore the same proctor mark as Captain's. She frowned. "Do all three of us answer the same question?"
What if one fails?
Sachiko smiled. "Isn't that faster?"
A wind sluiced the ruined street; goosebumps rose everywhere…
"Sir…" Gotoh glanced at Roy; Kuraging tipped her chin to him; Sachiko did as well—she'd already judged the boy was the axis here.
Captain said he can practice sword in a storm—counting on me not fighting. He's afraid I'll get hurt. But Sachiko never gave exam-takers a hard time. She always let them pass, right or wrong. If they erred and later got lost and met beasts—that wasn't her problem.
All eyes slid to Roy. He seemed far away, lost in himself. Then he focused, smiled, and said, "Granny, how about a deal—"
No.
Sachiko meant to refuse, but the "no" died on her tongue. The boy's eyes changed—two suns rose in his sockets, blazing down on her. She felt stripped bare in the street, seen to her bones. She swallowed and flicked a glance toward a camera hidden in a corner…
A bolt of static blinked—the feed caught those scorching "suns" looking right through it.
Even through the screen it stung.
"Ho-ho… cheeky brat, bullying a proctor."
On the airship, Netero felt the balance tilt back his way; his eyes lingered on Roy's reddening gaze—reminded him of another great "beauty": Scarlet Eyes. He asked, faintly careless, "What type is the kid?"
Eye-based Nen is rare.
Zeno: "He didn't test."
"He said it's his trump card. He'd rather take three lashes from his father than tell."
"Ho… still stubborn." Netero blinked; back on the feed, Roy had "warned" an eavesdropper and now waited on Granny's answer.
Sachiko hadn't expected such keen senses. After a beat, she relented.
Roy's smile softened. He bowed. "Don't mind me."
"Ask whatever; I'll answer whatever. If I'm wrong, we turn back. If I'm right…"
He straightened, eyes steady. "Please teach me how to Conjure 'Nen beasts.'"
So he'd seen through it. Sachiko eyed his staff-sword and chose to trust Captain's judgement.
"Very well."
She smoothed her mood and asked, "Listen. My question is: 'Mother' and 'Wife' fall into the water at the same time—who do you save?"
"I think you're mocking my master."
The classic of classics—no "correct" answer.
Gotoh's stare went lethal. Kuraging lifted her chin and looked to Roy. She was, against herself, curious which way he'd go.
Mother… or wife?
Both, and neither.
"5…4…3…2…1…" Sachiko counted.
Roy smiled and stayed silent.
Confidence drained from her face in an instant. Five seconds later she forced a smile. "Correct. Congratulations."
She beckoned Roy aside.
Gotoh: "…"
Kuraging felt her arms suddenly empty, oddly bereft. She shot the butler a look, then realized—and explained, "That question has no answer. Saying nothing is optimal."
"No need to remind me." Gotoh cut her a glare. With Roy and Sachiko talking, he hissed, "Then let's discuss—your overstepping…"
Kuraging: "…"
Frozen on the spot.
She swallowed, took two steps back—and fled after Roy…
Gotoh snorted and followed.
At the corner, the boy listened while Sachiko, voice marred by grief, recounted her awakening—how the orphanage burned, her mind went white—and all she wished was to save the children.
"Something opened in my heart… and when I came to, there was a doll beside me…"
She guided over the biggest child among them—first of her "dolls." "I named him Ryouta, to remember my child. Then came…"
"Fubuki… Shizuko… Juuro… Kenya…"
One child after another gathered, hemming her in.
She stroked heads and smiled faintly. "Later I met a man—he told me the thing I opened was Nen. My 'imagination' called the dolls forth…"
So—
Ask the Heart, then Imagine, then Practice.
Roy stroked his earring, recalling that night Tanjurō brought him outside, set the Hanafuda on his ear, patted his shoulder and said, "Good spirit." That surge of emotion—the unconscious Conjuration that followed…
So, as Sachiko said: if he wants, and shapes it from the heart, he should be able to turn aura into reality.
He stood still, thinking. Gotoh and Kuraging flanked him, Sachiko watched on.
"The harder the thing, the harder the Conjuration," she summed up. "Imagining a pen is easier than a car. From my experience—start small. Conjure something simple—and build your own 'Nen beast.'"
Something simple—for him?
Roy rubbed the staff-sword; a spark lit in his eyes. A blade.
That short blade on the wall at his teacher's home—the one he'd swung ten-thousand times a day. His companion in Demon Slayer. His brother—his bond…
He opened his palm, eyes brightening as aura swelled in his hand. He pictured the sword—the scabbard, grip, edge, tip, even the patterns etched along the blade—down to the last line—
In the Demon Slayer world…
With Roy asleep, Giyu wrapped up a detailed report to Ubuyashiki under Urokodaki's guidance. He hesitated—should he advise skipping the "tsuguko" stage and naming Roy as Hashira?
Urokodaki paused. "There's never been such a precedent."
"You can advise. As for the Master agreeing…"
He looked at the slumbering boy and smiled. "It won't matter."
"So long as Roy refuses—no one can force him. Not even the Master."
"Brother, your view?"
"I agree with Master." Sabito wrote with a floating brush: "From what I know, whether he joins the Demon Slayer Corps is irrelevant to Roy. If it kills demons, he doesn't care about titles—
Even 'Master'."
The brush halted; Sabito frowned…and added:
"Giyu, when you return—keep an eye out. Roy's not the sort to kneel. At meetings… I fear—"
"No fears," Giyu cut in coldly. "If he won't kneel—the other Hashira will give him trouble."
Faces fell in the lamplight.
One could already taste the chaos to come. In the hush, a humming tremor—everyone turned—and gaped—
On the south wall, Roy's short blade glowed faintly.
And then—vanished.