Ren wanted Yoriichi to be the lock that restrained him, a choice made to prevent Yoriichi's suicide.
To that end, he vowed to refrain from evil while Yoriichi lived, but that didn't mean the matter was settled.
As he'd said, the fate that befell Chitoshi would befall the Demon Slayer Corps' members.
Their deaths alone weren't enough—they had families.
Ren was no saint. After Chitoshi's death, his last shred of kindness vanished. The adage "calamity shouldn't touch kin" held only if his own kin remained untouched.
The Ubuyashiki clan likely sensed Ren's intentions. It wasn't impossible that Yoriichi had shared Ren's plans with them, being the only one who knew.
When Ren sought the Hashira's families, he found they'd been relocated, likely hidden at the Ubuyashiki estate for protection.
But the Ubuyashiki and the Corps didn't grasp the enemy they faced, nor the depth of his obsession.
That day, countless crows soared into the sky, scattering across the world.
They looked like ordinary crows, save for their blood-red eyes.
These crows were extensions of Ren's will, his eyes, monitoring every movement in the world.
They aided Ren in tracking the families hidden by the Ubuyashiki.
Late at night, in a dilapidated temple, a demon devoured its meal, scarlet blood pooling on the ground. Satisfied, it rose only when nothing remained.
Turning, it froze. A figure stood in the shadows behind it.
Shrouded in darkness, only the figure's eyes were visible.
"Hiss!" The demon crouched, baring fangs, alert as a beast.
The figure glanced at it, eyes marked with "Demon" and "Moon."
Instantly, the demon felt a primal suppression from its bloodline, collapsing to its knees, trembling.
"A demon without reason?" Ren muttered, frowning.
Demons had hierarchies.
Weak humans turned into mindless demons, no different from beasts. Lacking intellect or thought, they often attacked their own families first.
Next were rational demons, capable of thought but lacking great power. Against demon hunters, they relied on their bodies' resilience, but skilled Corps swordsmen easily dispatched them.
Higher still were demons who awakened Blood Demon Arts, the elite among thousands.
Ren sought such demons to fulfill Muzan's order to assemble the Twelve Kizuki.
But after years of searching, he found few worthy candidates.
In decades, he'd recruited only two or three for the Lower Ranks, and even those were barely adequate.
Muzan tasked Ren with completing the Twelve Kizuki. Initially, he thought it feasible, but now he realized its difficulty.
Frustrated, Ren glared at the cowering demon. "Useless," he scoffed.
Splatter!
The demon's head exploded like a melon, regenerating seconds later.
"Scram," Ren snapped.
The demon fled in terror.
Ren sighed, his face etched with vexation.
Watching the demon scramble away, he wondered if his approach was flawed.
Searching for demons Muzan had created to assess their Kizuki potential seemed futile—if they were worthy, wouldn't Muzan have chosen them already?
Perhaps a new strategy: instead of demons, find exceptional humans and turn them into demons. Wouldn't that be simpler?
Outside the temple, a crow braved the storm, landing on Ren's arm.
"I see," Ren said, his usually calm eyes flickering with rare emotion.
After decades, he'd found news of the Sound Hashira's family.
"I thought you could hide them forever, Ubuyashiki," he murmured.
Spreading his arms, Ren dissolved into countless crows, vanishing into the rainy night.
At night, on a desolate path, two children huddled in the bushes.
"Big brother, is it really okay to sneak out?" the younger girl whispered, timid. "Didn't they say something scary is hunting us?"
"You believe that kid's tale?" the boy snapped. "We've been stuck here for years, and they always say that. They just want to cage us. If we don't escape now, we'll never leave."
"But running off without a word feels wrong," she said.
"Then go back!" the boy growled. "I'm not returning. That Ubuyashiki guy claims he's protecting us, but we've seen no danger in years. Little sister, don't you want to go home? To see it again?"
"I… I do," she admitted, hesitating before grabbing his sleeve. "I'll go with you."
The boy grinned. "Heh, stick with me, and we'll be fine. I've watched this path for ages. Just follow it, and we'll get out."
The girl nodded. "Brother, that crow… why does it feel like it's staring at us?"
He turned, spotting a black crow perched on a branch, watching them.
It was just a crow, yet meeting its gaze sent chills through them.
The boy grabbed a stone and hurled it. The crow flapped away, and he smirked. "Nothing's watching us now."
With the crow gone, their unease faded.
The siblings crept along the path, unaware that the crow had returned, perched on the same branch, silently observing.