The preparations and adjustments required for this "Joint Expedition" were far more extensive than they appeared.
Even though the Loki Familia, Astraea Familia, and Hephaestus Familia had already formed a practical alliance, within the Hephaestus Familia this relationship was still unofficial and concealed.
That meant careful selection was required among the internal craftsmen who would be mobilized.
And by careful selection, it meant something on quite a different level.
Tsuna had to personally oversee the entire process, using his Mist to induce hypnosis, and his Memory Worm to verify the integrity of their memories.
Hephaestus herself would perform lie detection, while Tsuna confirmed the truth through memory examination.
Only after passing both tests could a member join the Joint Expedition's team.
This workload meant Tsuna had to stay within the Hephaestus Familia for several days, continuously conducting evaluations.
Under such relentless pressure, the once composed Hephaestus gradually turned darker and darker in mood—half her face seemed clouded in frustration.
"Good grief, I really didn't know… I had that many of my own children secretly planted here."
Plenty of Adventurers had slipped past Hephaestus's lie detection before—using a technique identical to Tsuna's own method: erasing memories to avoid triggering divine detection.
As long as they themselves possessed no relevant memories, they technically weren't lying.
And if it wasn't a lie, then a god's lie-detecting power couldn't take effect.
Unfortunately for them, this time's examination wasn't performed by Hephaestus alone—Tsuna's Memory Worm was also involved.
A lie might deceive Hephaestus's power, but it couldn't escape the subtle fractures left in their memories.
"Hephaestus, this isn't unusual," Tsuna said calmly.
It was, after all, within reasonable expectations.
"Many Familia inevitably form ties with production Familias. It's natural that some gods want firsthand information from within."
"And since they're all gods, they understand each other's abilities. Finding ways to bypass them is much easier than it sounds."
Hephaestus shot Tsuna an annoyed glance.
"You make it sound so simple."
"Besides," Tsuna continued, "many gods send people to your Familia because they value your craftsmanship. If it were some unknown smithing Familia, they wouldn't bother with such effort."
"That's true."
Hephaestus's tone softened. For all her irritation, she took pride in her skill.
In the heavens, she had stood among the top artisans, forging countless divine weapons that few could ever match.
Hearing Tsuna's sincere admiration soothed her considerably. At least her mood wasn't completely spoiled by the discovery of spies among her children.
"Then, should we drive them out?" he asked at last.
"Yes. Expel them. The upcoming Joint Expedition will involve your secret—and we can't risk them staying."
Since the mission concerned the concealment of Tsuna's power, Hephaestus could no longer allow those spies to remain. Otherwise, once the expedition ended, Tsuna's abilities would spread across the entire Labyrinth City.
Of course, there was a simpler way to deal with them.
They could just be "assigned" to the expedition roster. That would eliminate the hidden problem quietly—and even the gods who planted them wouldn't know whether their spies had been exposed.
But those children were still Hephaestus's children.
Killing her own children, even to root out spies—Hephaestus could never bring herself to do that.
So, driving them out was her only choice.
"After removing them, we'll need to be more careful when recruiting new members," she said. "Tsuna, I'll have to rely on you for that."
"No problem. Anyone with memory inconsistencies gets rejected outright."
A god's lie detection could be fooled, but memories could never be perfectly fabricated.
And no god would ever imagine that someone could detect memory discrepancies—let alone guard against them.
"Now, about the Joint Expedition itself," Hephaestus continued.
"Our Familia will act as support. Tsubaki will lead our craftsmen to aid the front-line Adventurers with weapon and armor maintenance. In exchange, we'll have priority rights to any materials gathered from the deep floors."
Materials—those were the lifeblood of a production Familia, especially one of craftsmen. Deep-floor resources were nearly impossible to come by.
After all, the materials from the surviving deep-floor monsters currently circulating in Orario were all remnants from the days of the Zeus and Hera Familias.
But no matter how carefully those reserves were managed, those two Familias had been gone for years.
Their stockpiles had long since run dry. If anyone wanted to forge stronger weapons now, they needed new deep-floor materials—there was no alternative.
Especially since Hephaestus and Tsubaki had recently used their accumulated Excellia to pioneer new forging methods, they now required a vast quantity of deep-floor resources to continue developing their craft.
"I imagine neither Miss Loki nor Lady Astraea will object," Tsuna said. "After all, weapons forged by you and Tsubaki will benefit them directly. As for discounts on new equipment, well… you'll have to negotiate that with them yourself."
"Ah, that part I'll handle," Hephaestus said with a wry smile. "But there's something else—something I need to discuss with you privately."
"With me?"
Tsuna blinked, not understanding what she meant.
Hephaestus lifted her left hand and pointed to the ring on her middle finger—the Mare Ring.
"The material that fuels this ring's flame—it doesn't exist in this world. If I'm to craft a weapon that can channel or draw upon that fire in battle, I'll need a supply of that same material."
"Not just me," she added. "Even Tsubaki, after receiving her own ring, is eager to study and replicate its forging material."
"That's… difficult," Tsuna admitted. "I'd have to wait until I can return. Right now, I can only faintly sense the spatial coordinates of that place—I still can't open the gate between worlds."
"Whether you can open it or not isn't the point," Hephaestus said, meeting his eyes with a rare smile. "When you can—take me with you."
"Eh?"
Tsuna stared at her, stunned. He hadn't expected that request from the Goddess of the Forge.