A/N: This chapter was written for the Sumigakure Halloween Event of 2016 prompt "Sneaky Creeping Shadows."

o.o.o.o.o

"There is nothing more dangerous than the darkness."

It was something Shikaku remembered his father telling him, and would tell his own son in turn. It was something every Nara learned from the cradle, that the shadows were control and craving, eating up the universe a speck at a time.

The Nara controlled the empty shadows, but they were the… curators, for lack of a better word, of the bottled darkness.

Or… whatever people wanted to call the creatures that preyed on whatever ventured away from the light. Shikaku knew the proper name, but it was so obviously foreign that no one ever used it.

Vashta Nerada.

The creatures weren't… they weren't naturally aggressive, from what the Nara knew. The problem was that the swarm that had nearly taken the planet hostage was vicious, hostile, and somehow tainted by the chakra in the air. Microscopic carnivores that took the form of shadows, the only way to handle them had been for three clans to band together, once upon a time, with information dealt by a man in a blue box.

The Nara clan was part of two distinct alliance groups. The more well-known, stronger, and friendlier was the InoShikaChou alliance, that of the Nara, the Yamanaka, and the Akimichi, in conjunction with a slightly weaker alliance with the Sarutobi. This alliance stretched back almost to the time of the Sage of the Six Paths.

The second group was smaller, quieter, unknown to almost all save for the involved clans, and select alliances of those clans. With the advent of the villages, their kage were informed as well.

When the Vashta Nerada first came to the planet, scattered in the wake of a metal craft that fell from the sky, three clans had led to the defeat of the creatures: Nara, Aburame, and Uzumaki.

Even without being literal shadows, there was enough dark to them that the Nara could have some control, if not with complete safety. Even without being a local species, there was enough insect to them for the Aburame to herd them where they would. Even without being born to chakra like the rest of the planet, there was nothing an Uzumaki could not seal.

So the Aburame could stall and corral. The Nara could force and shape. The Uzumaki could seal and contain.

And the man in the blue box had left them the information they needed to do it all again, if the supposedly unbreakable jars ever cracked open and let their occupants free into the world once more. The jars had lasted over three hundred years with almost no maintenance from the Uzumaki. The heir of each clan was given a warning seal tattoo on their second birthday, small and inconspicuous on the back of the wrist, something that would burn and tell them if the Vashta Nerada ever escaped.

Shikaku always had a feeling, in the back of his mind, that the jars would crack during his lifetime, and when Shikamaru was born, his greatest wish became that his son would be far, far away when that happened.

Unfortunately for Shikaku, nothing was ever easy. The seal did not go off and warn him in an otherwise peaceful period where he could afford to waste time literally hunting shadows. The seal did not even choose to go off in a tense but manageable period, or a crisis that could be temporarily put on hold so he could deal with the escapees.

No, the seals went off when the jars were crushed, and the jars were crushed by Pein.

o.o.o.o.o

On the day of Pein, a lot of things happened. Several people died (and were later brought back to life). Several people achieved new heights in their powers (and later bragged at length during reconstruction).

Four people cursed as their wrists burned, though only one was close enough for Tsunade to hear.

"Shikaku, that sure as hell better be good news." Tsunade warned, though the fatigue in her voice made it apparent that she held very little hope that was the case.

"The Vashta Nerada have escaped." He told her stiffly.

Tsunade's eyes widened, and her face paled. She turned sharply to Katsuyu. "Relay a message to all Nara and Aburame still capable of moving. Shikaku, you know these things better than I do. What needs to be done?"

"We need to corral them. We might be able to use them as a trump card against Pein, but not permanently." Shikaku wet his lips, considering. "We… we don't have anything prepared to capture them, Hokage-sama. The only Uzumaki in the village is Naruto, and he definitely doesn't know how to—"

"My grandmother was an Uzumaki, Shikaku." Tsunade reminded him with a wry, tired grin. The noise of the far-off battles was a harsh counterpoint to the mostly safe but nonetheless tense planning in the temporary command center. "I may not have been taught how to fight these things, but I know enough of sealing to get the job done, especially since Mito-baa-chan made sure I knew these in particular. Survive to the end of the battle, and…"

Tsunade frowned. "Actually, let me write those seals down now."

"Tsunade-shishou," Shizune protested. "The healing is more—"

"That's why I'm writing it down now, Shizune." Tsunade cut the woman off. "There's a good chance I'll be suffering from chakra exhaustion when this disaster is over. These creatures cannot be allowed free. If I write the seals down now, there's at least a decent chance someone else can take care of them properly later, whether I'm in shape to do it or not."

Shizune pursed her lips. "Yes, Tsunade-shishou."

"Shikaku, I want everyone in your clan that's even vaguely capable of handling these things on the job. Katsuyu, I want you to send that message through to Shibi as well. Get the message out to all members of both clans. They're pulled from the Pein battle in favor of the bottled shadows." Tsunade nodded to the slug on her shoulder. "Shikaku, anything else?"

"Tell everyone to count the shadows, even civilians. Seals on the shelters in the mountains should be on their highest security levels, if they aren't already." He remembered everything from the stories. "And contact an Aburame or a Nara the second it looks like they have more shadows than they should in whatever lighting they're in."

Tsunade nodded. "Check the immediate area before you go."

Shikaku closed his eyes, let his awareness stretch into his shadow and let the whole thing pool around his feet, subsequently spreading out to check every nook and cranny in the vicinity. If the Vashta Nerada were here, he would sense them.

"Clear, Hokage-sama," he said with a sigh. "I would feel most comfortable if you were to keep a member of my clan nearby to ensure your safety from the Vashta Nerada."

"Send someone who's got good control of your techniques, but isn't physically capable of being on the battlefield against Pein or wandering around the village looking for the escaped creatures, then." Tsunade waved a hand dismissively. "I seem to recall one of your Chuunin recently broke a leg. They'll do."

"Of course, Hokage-sama." Shikaku took care of that immediately, and he couldn't help but laugh grimly at the pinched looks he saw on the faces of both his own family and the Aburame.

The rest of Konoha had no idea what danger lies behind the shadows. They never had.

o.o.o.o.o

When the battle ended, Shikaku found out that Tsunade was in a coma, because of course she was.

"I guess she was right," Shizune said grimly as she handed over the seal schematics for the shadow jars. "These did end up being necessary."

"Don't exactly have a lot of seal masters to help implement them, though." Shikaku looked them over and winced. He wasn't completely unfamiliar with sealing, but fuinjutsu was never his strong point. "With Tsunade down and Jiraiya dead, we have… Kakashi?"

"A handful of medics, including myself, and some shinobi scattered about the ranks with varying degrees of competency, but yes, Kakashi would be the best suited for this." Shizune squeezed her eyes shut tightly for a long moment, and then relaxed. Sleep-deprivation, then. "There's also Danzo-sama, but—"

"No." Shikaku shook his head. "I'll see about asking Kakashi, then."

(It took only a few hours for a report to come in about a chuunin seeing her teammate step into some shadows and immediately turn to bone.)

(The Nara and Aburame began sweeping the village endlessly, searching for the lingering swarms they'd somehow missed. Three more corpses happened before they could finally say they were sure they'd gotten everything.)

(The four dead Konoha denizens weren't worth the one Pein Path the swarms had devoured.)

(It took Kakashi three days to prepare the jars, and Shikaku is sorely tempted to make a joke at the end that the shadows under the man's eyes were almost as dark as the ones they were capturing.)

(He didn't, because the bags under his own eyes were just as bad.)

(Besides, Genma made the joke for him.)

o.o.o.o.o

Naruto insisted on learning the seals, of course. With so few Uzumaki left, someone had to do it.

o.o.o.o.o

It was two and a half years after the Fourth War, two and half years after Shikaku's death, that he saw it happen. It wasn't uncommon for the dead to watch over the living, even if they couldn't do anything, and Shikaku watched his son, filled with pride and affection.

And then, one day, a man in a blue box came and held out a hand to Shikamaru, and to Naruto, and to Shino, and even as the others in their age group watched in confusion, the boys knew.

They knew the man in the blue box.

Shikamaru and Shino went, the seals on their wrists like tiny reminders of the stories they'd grown up with. Naruto, though, begged off. He still had so much to learn, and he hadn't… he wasn't… Naruto never did finish answering why he didn't think he could go.

He did offer up a substitute, though, someone he insisted was a lot better at "the brainy part of fuinjutsu and all that stuff, which is the important part, 'cause I'm pretty creative but it doesn't really matter when I can't really remember how different schematics work most of the time."

(Shikaku had met Uzumaki Karin all of one time, when Konoha first captured her after the assassination of Shimura Danzo.)

(She was… well, she was exactly the kind of catalyzing presence a lazy boy like Shikamaru needed, and the kind of deceptively loud-mouthed yet undeniably perceptive kind of person that a boy like Shino needed, and they were both the kinds of good, moral people that a girl like her needed.)

(As the box disappeared, Shikaku smiled to himself. Those kids would be fine.)

(And those shadows would stay chained.)