“The Vault?” echoed Jin, genuinely confused.

“The Vault,” Namjoon repeated with authority, large smiles spreading over both his and Taehyung’s faces.

“Oh man! You’re finally gonna let me see the Vault?!” the younger man exclaimed, jumping for joy.

“Yes, but Monnie stays here,” stipulated Namjoon.

Taehyung had scooped up the lizard, and was happily dancing around the crowded room, the dragon his unwilling partner as the boy swayed and dipped. Monnie hissed and spat, the glow in his chest already building in intensity as the frills on his head turned bright red.

“Uh…, Tae?” called Jimin.

The younger man was too busy singing about the Vault to pay any mind to his companion, however, and only took notice of the luminous lizard when it let out a burst of searing flame, narrowly missing the tips of Taehyung’s fiery hair. Jimin noted with amusement that the thin mental string that connected him to the dragon intensified slightly when the creature breathed fire. The cord was already dying back down, recessing to the corners of Jimin’s perception as the reptile’s chest itself visibly cooled.

“What is the Vault?” Jin pressed as Taehyung set down the disgruntled lizard.

Monnie scrambled over to Jimin, and dug at his clothing as it scaled the side of the young man’s leg. Taehyung crossed his arms and narrowed his eyebrows, glaring at Jin before shifting his attention to Namjoon.

“Don’t tell me he gets to go to the Vault, too!” wailed Taehyung.

“Well, I’m not leaving him here in my apartment alone,” stated Namjoon. “Besides, it’ll be fine; we can drop him and Yoongi off before we get to the actual Vault. There are a of couple empty rooms down there; perfect for holding possible Guardians.”

“Great,” Yoongi grumbled. “Now we’re even more like prisoners.”

The rest of the boys ignored him as Namjoon crossed the floor to a small door positioned on one side of the room. The portal appeared to be made of wood, and was much less intimidating than the permanently-locked metal barrier at the front of the apartment. Jimin had initially assumed that this particular door led to the bathroom or closet, but he quickly saw that that was most definitely not the case when Namjoon slid back a panel to reveal a keypad, which he punched numbers into at a lightning-fast pace.

✧✧✧

With a hiss, the door slid back into the wall - obviously no ordinary plank of wood - and shifted up to reveal a set of concrete stairs that descended into darkness.

“Put your shoes on, guys,” advised Namjoon. “I don’t want anyone stepping on something they shouldn’t.”

“This is so ing cool,” whispered Taehyung.

“Promise me you won’t break anything, okay?” joked Namjoon as he started down the stairs.

“Why does everybody always ask me that?” mumbled the younger man, nearly falling over as he hopped while pulling on his sneaker.

The entire group was walking down the staircase now, the sounds of their footsteps reverberating off the stone walls. The stairwell looked uninviting and ancient, which was very different from the homey but messy apartment above.

“You’re one to talk about breaking things, Namjoon,” taunted Hoseok. “Remember when Tae dragged you along on one of his ridiculous monster hunting missions and you almost demolished half of the building you were in?”

“A building that was scheduled to be torn down the following week, might I add,” defended Namjoon. “Anyway, here we are, so let’s leave that argument for another time, okay?”

The men had reached another door at the bottom of the long set of steps, and this one was much more harrowing in terms of appearance. Namjoon tapped at another keypad, and the entrance unlocked with an mighty, echoing click.

“After you,” Taehyung told Hoseok with mock politeness, and the older man shook his head as he followed Namjoon through the door.

Jimin had been expecting another decrepit room nestled deep underneath the streets of Seoul, but the office-like atmosphere of the area he stepped into surprised him. There were several men and women at work stations inside a row of ugly, monochrome cubicles, and some of them even waved to Namjoon as he and the gaggle of men passed through.

The purple-haired man led them into a room with more people milling about - a large staircase the focal point of the high-ceilinged space. If not for the concrete walls and harsh overhead lighting, the entire area would have looked like a grand entry hall, with several connecting passageways branching off from its center.

“Everyone has to go through that dingy little apartment to get here?” marveled Jungkook.

“There’s a main entrance,” laughed Namjoon. “I just have my own backdoor.”

“What; you’re not the receptionist?” teased the younger man, giggling.

“Ew, no. That’s my sister’s job.”

✧✧✧

The people in the main lobby were dressed in skirts and ties; their attire business-like although not overly formal. Some even had what appeared to be identification badges pinned to their lapels, and all of them looked to be in a perpetual rush. It was easy to pick out who the Sensors were in the crowd, as they were prone to staring oddly at Jin as the group advanced toward a tunnel on the far side of the room.

“What are all these people here for?” wondered Jimin. “They’re not all Sensors, right?”

“Right,” replied Namjoon. “Though some of them are. As for what they’re doing… well, most of that is classified. Truthfully, I don’t even really know myself - my father is in charge of all the research that goes on down here.”

“Research?!” Taehyung shouted a bit too loudly, drawing the attention of several passersby. “You mean I could have been working in a super cool underground bunker this entire time, and instead I’ve been living out of my car for the past three months?!”

“It’s pretty hard to get an invitation to work here,” revealed Namjoon. “There’s a whole grant process and everything - it’s all kinda complicated.”

“WHY doesn’t anyone tell me about these things?” groaned Taehyung as they filed into the narrow hallway.

“There’s still a lot of stuff even for you to learn, Tae,” reminded Hoseok. “You say it yourself all the time.”

“Yeah, but imagine how much more I could learn about cryptids if I could work in one of the labs here,” moaned Taehyung.

“There’s some dangerous stuff down here, Tae,” explained Namjoon. “We don’t usually let just anyone run around the place, y’know? I’d be in a huge amount of trouble just for bringing you all down here if anyone found out about it.”

Jimin glanced nervously over at Jin and Yoongi, but the former was expressionless while the latter was staring up in awe at the fluorescent lighting. There were certainly more than a few worrying strings leading Jimin’s subconscious in several directions as they continued their way down the empty tunnel. He hadn’t had much of a chance to focus on the perceivable monsters  when he had been above ground, but now that Jimin took a moment to concentrate, the young man could feel some very malevolent presences - one of which he was certain had rows and rows of rotting, flesh-laden teeth.

“I hate to lock you up like this,” Namjoon proclaimed as he fiddled with the keys to yet another heavy door. “But, like I said: dangerous stuff, trade secrets, shouldn’t even be down here. I think it’s best if I keep you guys here until we get back from the Vault.”

He swung open the door to reveal an extremely sparsely-furnished room, with nothing but a card table and chairs sitting under an exposed lightbulb in the middle of the room.

Jin seemed reluctant, but stepped inside without complaint. Yoongi was slightly more vocal about his displeasure, muttering unintelligibly as he followed after the oldest man. Jimin wanted to follow them, but was unsure if he was supposed to do that or go with Namjoon to the Vault.

✧✧✧

“Jimin, I guess you can either stay or go,” offered Namjoon as if he had read the other man’s mind. “It’s up to you.”

The confused young man stood just outside the doorway, glancing rapidly between his angry-looking, older friends and his clearly excited, newer acquaintances. Some of the initial shock that had surrounded learning that Jin was some kind of mythical creature had worn off over the past several hours, but Jimin was still eager to get a chance to speak with the older man. On the other hand, he feared that he wouldn’t be able to get any answers out of Jin while still in “enemy territory,” so to speak; plus he wanted to see what the Vault was, too, and whether or not it could help solve the mystery of why Jimin was the only Ultimate Sensor in Namjoon’s database. Jimin felt torn between nostalgia and novelty; completely unsure where his loyalty should lie.

“Jimin and Jungkook are coming with us,” announced Taehyung assuredly. “We’re looking up their family histories, so it’s only fitting that they get to accompany Namjoon and I to the Vault. Hobi can stay here and guard those two.”

“What makes you think you get to see the Vault?” tortured Namjoon.

“B-but! You said I could!”

“Relax, Tae,” chuckled Namjoon throatily. “I’m just in’ with ya. Of course you can still see the stupid Vault.”

“Yes!” screeched Taehyung. “God, I’ve only dreamed of this day. And now, here I finally am: two stories underground in a top-secret bunker with a Guardian in our midst and a mystery that can only be answered by THE VAULT!”

“Let’s hope so,” agreed Namjoon. “Hoseok, are you okay with staying here?”

“Yeah, yeah,” complied the older man. “Let Tae have some fun. I remember my first time seeing the Vault.”

Taehyung had been twirling around, jumping as he danced wildly in anticipation of seeing the Vault. He stopped now, though, to stare open-mouthed at Hoseok, who returned his look with a satisfied smirk.

“What? You’ve been down here before?!” howled Taehyung. “Who in their right mind would let you into the Vault?”

“Of course I’ve been here,” scoffed Hoseok. “Jimin and Kookie are probably some of the only Sensors in the country who haven’t.”

Taehyung was silent for several moments before he exploded, pacing down the hall as he left the other six men staring after him.

“EVERY ING TIME! Nobody tells me anything!”

Jimin stared at his feet while he listened to Taehyung’s tantrum fade as the latter moved farther down the hallway. He didn’t let his eyes leave his sneakers as he mumbled his accordance, too afraid to look at anyone.

“Guess I’m goin’ to the Vault with you, then.”

Namjoon offered an empathetic smile as he closed and locked the door, leaving Hoseok with the two imprisoned older men. Jimin could still sense Jin’s tether through the thick door, and he wondered if the barrier would be enough to hold the latter inside should he make up his mind to leave. He remembered that Jin had been unable to break through the front door of Namjoon’s apartment, however, so Jimin thought it likely that whatever the powers Jin might possess, they wouldn’t be enough to allow him to escape.

“No time to waste,” urged Namjoon as he set off down the hallway behind Taehyung. “If we’re gonna do this, then let’s get going.”