"The 'Other Side' is what we call the Immortal Realm," the one-eyed boy said.
"...What?"
For a moment, I thought I had misheard him. But no—I definitely heard the word "Immortal Realm."
"Are you saying... the Immortal Realm exists?" I asked, still trying to process his words.
"Of course! Around these parts, it's common knowledge... or so I thought," the boy replied with a shrug. "I mean, you're a mage, right? Didn't you come here to get a sword made?"
"Well... yeah," I admitted reluctantly.
I didn't feel like explaining how the blacksmith had refused to forge anything for us. It didn't seem relevant to this strange conversation.
Unbothered, the boy continued with enthusiasm. "That blacksmith—he's what we call the 'Gatekeeper.' He maintains the balance, keeping this world and the Immortal Realm separate. He's the key."
"The old man? Really?"
"Old man, huh? Hah, he must be pretty up there in years now. When I first met him, he was just a little kid," the boy said, gesturing to indicate a height no taller than my knees.
Wait, was he serious? That would make the blacksmith about three years old when they met. Surely he was exaggerating—but in the world of exorcists, it wasn't unheard of for kids to start training that young.
Still, I couldn't quite wrap my head around what this boy was saying. I had more questions than answers.
"Hold on, are you telling me that blacksmith is responsible for keeping the Immortal Realm separate from our world? Why?"
"Ah, you're a sharp one. Surely you know—Immortal Realms expand, don't they?"
"...No, I didn't know that," I replied, frowning.
This was the first I'd heard of it. Harunaga hadn't mentioned anything about this when I spoke to him. Why did everyone assume I knew these things?
The boy seemed surprised by my ignorance, rubbing his chin thoughtfully. "Huh, so the oral traditions have been lost... well, that makes things tricky. Guess I'll have to explain it. But first..." He gestured toward the trail we'd just walked up.
"Take me to the blacksmith. We're running out of time."
"Why don't you just go there yourself if you know the way?" I asked skeptically.
"Can't cross the barrier," he admitted bluntly.
Oh, right. There was a barrier in place. I'd forgotten about that.
"So you can't release any more magic?" Aya-chan asked.
The boy nodded solemnly. His explanation made sense, but it raised another question that had been bothering me.
"You said earlier that people would die if the Immortal Realm expands. Why?"
"Because monsters from the Immortal Realm would spill into this world, cloaked in its magic. They'd devour humans left and right—a 'Night Parade of a Hundred Demons,' as they call it," he said grimly.
At those words, I felt Nina-chan, walking on my other side, stiffen. I gently rubbed her back to reassure her as I processed what he'd said.
So, the Immortal Realm was like a water balloon, constantly filling up with magic. Normally, it would let out just enough magic to maintain balance. But now, for some reason, the balance had been disrupted.
Letting out too much magic could cause disasters, but not letting it out at all would lead to the Immortal Realm bursting, unleashing a flood of monsters.
...This was a no-win situation.
"What's the solution, then?" I asked.
"The Gatekeeper, of course," the boy replied. "When the balance breaks, it's usually because something's gone wrong inside the Immortal Realm—a 'Demon Blight,' as we call it."
"Demon Blight?"
"A corrupted being within the Immortal Realm. If you purify it, the balance will be restored."
"So we just need to exorcise this Demon Blight?"
"Exactly. Just like how your body fights off infections. The Immortal Realm is alive, in a sense, and it works the same way."
That made sense, I supposed. The Gatekeeper—the blacksmith—was like the Immortal Realm's immune system. But...
"Problem is, the Demon Blight we're dealing with now is a Rank 5 Class-C. Not exactly easy to exorcise."
The boy stepped onto the mountain trail leading to the workshop. Dad, who had stopped to retrieve a sword from the car, followed close behind.
"The trouble is," the boy continued, "the Gatekeeper isn't doing his job this time. We've got to deal with the Demon Blight before it's too late, but..."
As we passed through the barrier, the scene that greeted us stopped us in our tracks.
"...Huh?"
Lying just outside the workshop, clutching his chest, was the blacksmith.