Haruto had never heard the term Ghoul Eater before. Perhaps Ubuyashiki knew, but he couldn't write to him now.
The term came from a bullet comment; Haruto would have to wait for it to appear in real life, otherwise he couldn't explain how he knew about it.
Ghoul Eater.
Someone who devours demons.
How does one devour? Literally?
During his time living with Genya, he knew the boy had an exceptionally keen sense of taste; he could distinguish every seasoning Makomo put in the soup with just one taste.
But what did taste have to do with this?
Haruto had an idea.
So, the next time Sora brought a mission, he waved at the dejected Genya: "Want to come with me?"
"Are you kidding me?" Sabito looked at him strangely. "Genya is still a child!"
"I'm already eight years old, I'm not a child anymore!"
Genya scrambled up from the ground, gripping his old nichirin blade tightly: "I'll go!"
"Don't worry, Sabito, I have my reasons. It won't cause any trouble."
Haruto nodded at the gentle boy, then patted Genya's smooth head: "Can you keep up with me? I won't stop and wait for you."
Though a bit nervous, Genya nodded heavily: "Of course I can!"
Haruto didn't expose his bravado, put on his haori, and led Genya down the mountain under Sabito's worried gaze.
The mission location wasn't far, also within Tokyo Prefecture.
A demon had attacked a farmer, killing many cows and the owner of the house.
This demon's power wasn't even comparable to a Lower Moon, and Haruto easily subdued it.
But the problem now was how to trigger Genya's ability.
Ghoul Eater—did it really require devouring demons to activate?
Haruto looked disdainfully at the dirty demon on the ground. Wouldn't eating this cause diarrhea?
Before, demons ate humans; now it's reversed, and humans are eating demons?
He sighed, held his blade horizontally, and prepared to sever the demon's head.
Perhaps by some divine will, Genya walked over and squatted beside the demon. He licked his lower lip, his movements hesitant.
"What are you doing?" Haruto asked.
Genya was silent for a moment, a hint of struggle in his eyes.
"He seems to provide me with… energy."
"Who?" Haruto raised his voice. "The demon?"
Genya swallowed with difficulty: "I don't know why, but a voice in my head is telling me to eat it… Teacher, I haven't been possessed, have I?"
Compared to those bullet comments in my head, I'm the one who seems more possessed.
Haruto scratched his hair: "You—did you have this feeling when you saw your mother before?"
At the mention of his mother, Genya's head drooped slightly: "At that time, my mind was full of fear and despair; there were no other thoughts." He looked up: "Teacher, let me try. Perhaps that's why my body can't use Breathing Technique."
Since things had come to this, Haruto also wanted to know what a Ghoul Eater's physique was like. So he picked up the half-dead demon, put it in the farm's water tank, and thoroughly washed it.
The demon, having listened to their conversation for a long time, shrieked in alarm: "What are you doing? What do you mean? What kind of ridiculous notion is 'humans eating demons'? Get it straight, I'm a demon and you're humans, you are the food!"
After so many years as a demon, he had never heard such an absurd idea!
"Should we use some soap? He's been in and out of water and dirt; he might have some germs on him," Haruto still felt uneasy.
"What do you mean 'in and out of water and dirt'? I'm a demon, not a mole!" The demon flailed its claws, trying to break free from the swordsman's restraint, but could only submit to the powerful force.
"It should be fine." Genya was also a bit nervous. He licked his lips, opened his mouth, and bit into the demon's arm. With a fierce tug, he tore off a piece of demon flesh, not even daring to chew, and swallowed it whole.
"Ow, ow, ow! You're serious?!"
The demon cried out in panic. Was this world too crazy? Humans not only didn't run from demons, but actually started eating them?
Haruto stared intently at Genya's reaction. Although the bullet comments were so certain, he had never seen such a person in real life.
Genya licked his blood-stained lips, then suddenly froze, veins crawling up his neck from beneath his collar.
Haruto immediately severed the demon's neck, then lunged forward to hold down his young apprentice: "Genya?!"
He had never seen a demon transform, but he imagined a demon's transformation would be something like this.
Genya's eyes were tightly shut, his whole body trembling, as if something was breaking out of him.
His entire body was covered in bulging veins, and two fangs grew from between his trembling lips.
Genya suddenly opened his eyes. His previously clear, clean whites had turned completely black, leaving only pinprick pupils, which were now staring fixedly into Haruto's eyes.
It's over! Haruto's heart sank.
Isn't this demonification?!
Genya… turned into a demon?
Haruto's hand gripped Genya's collar tightly, his mind already racing for remedial measures.
Is it that easy to turn into a demon?
According to the information the Demon Slayer Corps possessed, all demons were created by Kibutsuji Muzan and his Upper One of the Twelve Kizuki. They had to receive Kibutsuji Muzan's blood to become a species of his kind.
Lesser demons had no right to turn humans into demons. Let alone eating a mouthful of flesh, even if someone devoured them alive, it would be absolutely impossible to bypass Kibutsuji Muzan and become a demon.
Haruto forced himself to calmly observe.
If things truly reached an irreversible point, he would have no choice but to… "I'm fine."
Genya suddenly spoke.
Those pinprick eyes moved within their black sockets, as if adapting to this body.
"I don't believe it," Haruto said bluntly.
Sharp demon fangs, clinging veins, terrifying black eyes—none of it looked like he was fine.
"My mind is perfectly clear right now; I have no desire to eat humans."
Genya raised his hand high, licked his fangs with his tongue, and then looked at his palm: "My heart is beating so fast, and power is constantly surging through my body…"
Haruto hesitated, then tried letting go of him. Genya stood up from the ground and performed a set of sword techniques with his nichirin blade.
Wherever the blade went, it cut through the air, a vast improvement over his previous swordsmanship.
Haruto finally confirmed that he remained rational and let out a sigh of relief.
Soon after, the black in Genya's eyes receded, and the veins also subsided, though the two fangs still protruded from his mouth.
"It might be because this demon's power was too weak, so it didn't last long," Genya explained.
A few days later, the fangs also fell out.
Haruto wrote a letter to Kagaya, detailing what had happened to Genya and asking if he knew any demon scholars.
A few days later, Sora brought a reply.
"In the history of the Demon Slayer Corps, I found a physique very similar to Genya's: Ghoul Eater.
This is a special ability that temporarily turns one's physique into that of a demon after eating a demon or a part of a demon's body.
The stronger the demon he eats, the stronger his regeneration and power will become. He can even use Blood Demon Art he once used after further demonification.
The last time this physique appeared was 300 years ago.
As for the demon scholar you are looking for…"
Haruto could imagine Ubuyashiki's upturned lips just by reading the letter.
"The ones who know demons best are, of course, the demons themselves.
Go to Asakusa in Tokyo Prefecture and find a woman named Tamayo; she will be expecting Genya's visit."