The battle broke out without warning.
It started with fireballs.
"Gyahaha!"
Accompanied by a mocking cackle, a massive sphere of flame manifested and began a slow, deliberate advance.
The move was the same as before, but the circumstances had changed. The fireball was now large enough to fill the entire cave passage, leaving no room to retreat.
I stepped forward once again.
I projected a vertical barrier from the tip of my sword, punching a human-sized hole right through the center of the massive conflagration.
"Gyahah—I thought as much!"
"Hm."
A voice echoed from above.
His body was swathed in flames, but half of his face remained that of Jelasis as he clung to the ceiling of the cave. He was being clever—positioning himself so that he appeared as an ordinary Scorching Majin from Alicia’s perspective while revealing his true face only to me.
Jelasis, now a man with a half-human visage, spoke.
"You won’t choose the option of fighting alongside Alicia."
"...Since you're showing your face, is this the real you this time?"
"I wonder."
Fireballs swirled around Jelasis like eerie will-o'-wisps before hurtling toward me.
The air roared as I dodged the endless barrage, deploying a barrier beneath my feet to propel myself into the air. Jelasis countered with a flame-shrouded dagger, and our blades met with a harsh, metallic screech.
"You really are quite strong," he admitted.
"Obviously."
I had survived this brutal world using nothing but barriers. Even if I could use other types of magic, even if I had studied them... everything was ultimately for the sake of perfecting my barriers.
"But you’re exhausted, aren't you? I wonder how much longer you can keep this up. Gyahah!"
"Tch."
Jelasis shifted back into the form of a Majin made entirely of fire. The heat erupting from his body was even more intense than our last encounter.
"Gyahahahahaha!"
The flames surrounding him expanded until the entire area felt like a sea of scorching heat. My barrier finally reached its limit; it could no longer fully withstand the density of his magic power and thermal energy. I felt the skin on my face begin to sizzle.
"Hey, Jelasis—"
As my breathing grew labored, I took a deep, deliberate breath. I drew the heat and the magic power through my lungs and into my body. It was hot enough to sear my chest, and it was painful, but it wasn't anything I couldn't endure.
"...?"
I spoke to Jelasis, who tilted his head in confusion at my behavior.
"—Did you really think you could kill me just because I’m tired?"
I immediately overhauled the construction of my barrier. I had memorized his magic. I was used to it now.
I narrowed the focus. I limited the barrier’s target exclusively to the magic power possessed by the Scorching Majin before me. I limited the defensive attribute strictly to fire.
I took a heavy stride into the sea of flames.
"...Why?"
Seeing me walk through the inferno with an indifferent expression, Jelasis tilted his head again. He reflexively reverted half of his face to question me.
"I can tell your magic reserves are low."
"Even if it’s just the leftovers, it's more than enough for the likes of you."
The logic was simple: I had stripped the barrier of its versatility. A barrier’s magic consumption can be drastically reduced by simplifying its parameters. If you try to account for every possible variable, maintenance becomes an ordeal. However, if you narrow the focus to an extreme degree, the barrier becomes significantly stronger.
What I had just reconstructed was focused solely on Jelasis's specific magic signature and the fire-attribute. I called the process Optimization.
It would let any other attack through, but it would never allow this specific man's magic or flames to pass. It is normally difficult to construct a barrier tailored to another person's magic, but I had already come into contact with his three times. My barriers excel at sensing.
That was why I had studied all sorts of magic and learned to use them reasonably well—so I could understand the foundation of the magic I touched and adapt to counter it.
"Your heat won't work on me anymore."
Now that we had reached this point, we could settle things with pure swordsmanship.
"You're just acting tough," he spat.
"Look who's talking."
Since I couldn't use the barrier I was wearing for offense, and deploying a separate offensive barrier was currently a strain, he was right—I was acting tough. But I wasn't about to admit that. Besides, there was nothing wrong with acting tough in front of someone important. We were students. It was a sensitive age; acting a bit cool felt more appropriate for the role.
"What happened to that confidence? Is this all a Demon-possessed is capable of?"
"Grr..."
As our blades clashed, the composure drained from Jelasis's face. And for good reason. I had a sword; he had a dagger. Normally, a maneuverable weapon would allow him to leverage his fire-attribute, wearing his opponent down with heat until they grew sluggish enough for him to slit their throat.
But here, against an opponent who could ignore his magic entirely, that advantage didn't exist. Instead, he was being steadily cornered by the overwhelming difference in our reach.
"You're a virgin, right?" I asked.
"Are you trying to rattle me with such pathetic insults?"
"That sort of thing should be saved for the person you love. I’m not some beast."
I countered his gaze. "Let me ask you instead: which of us is the monkey in heat? You gave me that smug, triumphant look when you talked about your kiss, didn't you?"
I stepped in deep and lopped off Jelasis’s arm. Blood sprayed with a wet thud. It was a shame—I had aimed for his neck, but a sudden burst of flames from his shoulder had knocked my aim off.
"Who was your first kiss with? Was it Patricia?"
"..."
Jelasis glared at me, silent.
"So I hit the mark."
That was rough. That woman was a specialist in fools who only knew how to manipulate idiots. In other words, Jelasis was a grade-A idiot.
"What could you possibly know?"
"Nothing. And it wouldn't matter even if I did."
In this place, we were enemies. He was the one who had gone out of his way to declare war, after all.
"It looks like I can actually kill you by cutting you this time."
"I don't know how you're neutralizing my heat, but your barrier has one flaw," he rasped. "You can't use it to attack."
"And?"
"Even if I lose an arm, I can compensate for it with magic. I still have the advantage!"
Flames erupted from his body like a rocket engine as Jelasis began to move.
"Gyahahaha! Right now, you're just a human!"
Once again manifesting as a Majin of scorching heat, he replaced his severed arm with fire and began to fly through the cavern, darting along the walls and through the sea of flames with total freedom.
"Oh, impressive," I remarked.
"Gyahah, die—!?"
Jelasis’s movements came to a sudden halt. It was because our eyes met.
"Back in the forest, there were plenty of things that tried those kinds of tricks."
He had likely intended to disorient me with his speed and attack from a blind spot, but if I knew he was coming, it wasn't an issue. During my time fighting in the forest, there were both enemy soldiers and monsters that used the trees to perform similar flanking maneuvers. If I simply held my sword out where they were going to be, they would impale themselves and die.
Since his projectiles were useless against me, I didn't even need to track him with my eyes; I only had to turn toward the strongest sensation of killing intent. Since I was already neutralizing his flames, the situation was no different than those hunts in the woods.
"Gah... hugh..."
Jelasis coughed up blood as he looked down at the sword buried deep in his chest. However, the light in his eyes hadn't faded.
"I’ve... caught you... Now I can kill you... I told you... the advantage was mine..."
"Just die already."
I twisted the blade, but Jelasis didn't falter. He gripped my arm, ensuring I couldn't pull the sword out.
"Burn, O Madness; be scorched from within by the Flames of Envy—"
As the incantation left his lips, I felt a surge of scorching heat welling up from the depths of my own heart.