Everything Ineffective Comes Down to Insufficient Firepower

After spending these past few days together, Tanjiro had come to trust Dan Lei's words.

After all, as a "mountain savage" from the Taisho era, Tanjiro considered anyone in the area who could read and write a man of culture.

With Dan Lei's knowledge, he was practically a Doctor. What was more, Dan Lei often taught Tanjiro little physics tricks to win him over, and had even taught him the multiplication table. Tanjiro was almost starting to see Dan Lei as his master.

So, with the demon immobilized by Dan Lei, Tanjiro conscientiously took Nezuko to dig for tools in the temple's backyard.

Meanwhile, Dan Lei gave a strange laugh and transported the unknown demon straight into the courtyard, pondering where to start cutting.

But the demon was a chatterbox. Even after being captured alive, it kept running its mouth.

"Hey, what the hell is wrong with you? What kind of sorcery did you use to immobilize me? Are you one of those legendary demon hunters? But why is your aura so strange? You don't seem human!"

Dan Lei had never expected a demon to tell him he didn't seem human. He promptly waved a hand, conjured a sharp ice blade, and cut off the demon's head, hanging it by itself from a nearby tree.

Even after that, the demon kept yammering.

So Dan Lei took out the paper and pen he had made with Magecraft and wrote down his observations.

"The instant its head was physically severed, it rapidly formed a small airflow system in its damaged throat. This proves that demons can consciously generate or modify their internal organs."

"The bleeding stopped in less than three seconds after decapitation. The blood loss wasn't significant. Its regenerative ability is stronger than that of an ordinary Dead Apostle, putting it at the level of a high-grade Abundance Monstrosity."

When he was done, Dan Lei casually cut open the demon's chest and abdomen, exposing its internal organs, then wrote down another observation.

"Its heart is beating, but it's blackened, with a clearly defined tissue structure. Black, unidentified patterns have appeared in its esophagus and stomach. Presumably, these developed to improve its ability to absorb and convert the magical energy in flesh and blood."

Even without its head attached to its body, and despite being unable to feel pain, the demon was horrified by Dan Lei's actions.

After all, watching oneself being cut open would terrify any intelligent creature, even if it knew it wouldn't die.

But without the threat of death, the fear didn't grow overwhelming. The demon turned its fear into anger and began cursing Dan Lei.

Dan Lei responded by completely sealing the airflow passages below its neck and every opening on its head with ice. With no air flowing through, it could open its mouth as wide as it liked and still couldn't make a sound.

Then Dan Lei lifted the top of its skull, saw the brain still alive inside, and promptly pried it out with his ice blade. He froze it and tossed it onto the ground.

The demon, which had been moving just moments before, stopped as soon as its brain was removed. Even its body ceased struggling. But soon, a new brain grew inside its skull, and the top of its head regenerated as well.

Remembering the demons in the story that could grow heads directly from their bodies, Dan Lei made another note.

"Removing the brain can temporarily halt all of a demon's activity, but it will quickly grow another one. The new brain doesn't necessarily have to grow in the head region."

Since this demon was low-ranking, it wasn't the one to study if he wanted to learn about Blood Demon Arts.

And after regrowing its brain, it seemed to have become a little smarter, too. Two arms and hands sprouted directly from its neck, and it began picking at the ice on its head. Once it had cleared its ears, it started cursing Dan Lei again.

Dan Lei promptly bound its two little hands with Magecraft Threads, resealed the openings with ice to silence it, and cut off one of its legs to test how much damage his Magecraft could really inflict on a demon.

After a barrage of fireballs, lightning, and ice spikes, Dan Lei concluded that his ordinary elemental attacks couldn't completely destroy all the demon's cells.

To kill a demon this way, he would have to damage it until its internal energy was so depleted it could no longer regenerate. Otherwise, he'd be left dealing with a body that could multiply without limit.

At that moment, someone emerged from the woods and spoke slowly.

"You can't kill a demon using methods like that alone."

This was the person Dan Lei and Tanjiro had been looking for: Sakonji Urokodaki, the Demon Slayer Corps' former Water Hashira.

He had arrived while Dan Lei was performing brain surgery on the demon. Kojiro Sasaki, in his Spirit Body form, had alerted Dan Lei at once.

However, Dan Lei had told Kojiro Sasaki to keep watch and leave the man alone, which was why he had been able to watch until now.

In response to Sakonji Urokodaki's words, Dan Lei silently drew a Magecraft array with the demon's blood, cut off a fresh leg, and tossed it inside.

The next instant, the Magecraft array activated, and the leg vanished in a puff of ash.

Dan Lei turned to Sakonji Urokodaki with a smile.

"It's not that complicated. Demons are still subject to the law of conservation of energy. Drain their magic, and their bodies disappear immediately.

"Of course, this demon is also very weak. Its body is terrible at containing energy, and it doesn't have much to begin with, so it was drained in an instant."

When he was done, Dan Lei turned back to the demon's body.

"Actually, elements can hurt demons just fine. Everything ineffective comes down to insufficient firepower."

With that, Dan Lei poured a little more of the demon's blood beneath its body and drew another Magecraft array. Blue-white flames burst forth.

This was the Magecraft array Aoko had taught Dan Lei to use for smelting metal when making puppets. In his previous life, Dan Lei had only been able to raise the flames to just over 800 degrees. Aoko had to handle the metal smelting for many of the high-grade puppets herself.

But now, Dan Lei raised the temperature to 2,000 degrees in an instant. It consumed a great deal of his magic and couldn't be sustained for long, but it was enough to show off.

Under the 2,000-degree heat, the demon's body vaporized in an instant. Its bones rapidly carbonized, becoming completely lifeless.

At that moment, Kojiro Sasaki appeared at Dan Lei's command and tossed the demon's head, which was hanging nearby, into the flames.

As soon as its head burned up, the demon died instantly. Even the brain frozen on the ground turned to Black Ash.

When it was done, Dan Lei extinguished the flames of the Magecraft array and turned to Sakonji Urokodaki again.

"You see? That's how you burn a demon to death.

"Also, if you could bring down an actual thunderbolt, it would definitely kill a demon.

"And I've already confirmed that elemental attacks can effectively kill demon cells and weaken their defenses. That's also why your Breathing Techniques are more effective at killing demons when they imbue your swords with an element."

By then, Sakonji Urokodaki was sweating profusely. If not for the mask covering his face, Dan Lei would have seen the corners of his mouth twitching uncontrollably.

After a long silence, Sakonji Urokodaki came to his senses and bowed slightly.

"I am Sakonji Urokodaki. It's a pleasure to meet you, foreign friend Lord Dan Lei, and you, Lord Kojiro Sasaki.

"Giyu Tomioka has told me about you both. You are truly extraordinary individuals.

"Mr. Dan Lei, I'm astounded that you can use flames like Divine Fire to burn demons to death.

"Lord Kojiro Sasaki is even a mighty warrior of the Heavenly Human Realm. I'm humbled by the difference in our abilities."

Preventing a demon from making a sound is like deliberately blocking your throat with the base of your tongue. That way, you can't make a sound at all.