Rengoku calmly observed the dazed Jin and then flicked his forehead to bring him back to reality.
"Itai!"
"Why did you do that?"
Jin massaged his forehead and looked at him aggrievedly.
"Don't space out when I'm in the middle of an explanation. You've only heard the advantages of your power, but there's also a severe disadvantage."
"And what's that?"
"Your physique is not suited for any of the breaths derived from Sun Breathing. Because of that, you won't be able to master any of them to their highest potential."
"In conclusion, you will have to develop your own breathing style—one that suits you. For that, you must first learn the basics of the five primary forms: Water, Flame, Wind, Stone, and Thunder."
"I will teach you the basics of Flame Breathing over the next five days. After that, you must practice and refine it on your own. As for the rest, you can only learn them after passing the Final Selection."
"Before that, you should know that some demon slayers possess greatly enhanced sensory abilities. You need to find out if you have any, as they can significantly increase your battle prowess."
Jin began reviewing his predecessor's memories and discovered something he had overlooked earlier.
"I have pretty good eyesight. I remember my father always asked me to keep an eye on the cattle because I could locate them from kilometers away."
"Hm. Once you can control the flow of universal energy in your body, try testing your eyesight again by channeling some of that energy into it."
"Understood. I'll try."
"Now, it's time to tell you the main reason I called you here. What do you think was the purpose of the demon who attacked your family?"
"Isn't it the same as why any demon attacks humans?"
Jin asked, confused. Rengoku shook his head and raised one finger.
"First, twenty-seven families are living in those mountains, yet only your family was attacked. And your family members were only killed—not devoured."
A bad feeling crept into Jin's heart. Rengoku raised a second finger, his expression hardening.
"Second, the demon who attacked your family was one of the Demon Moons—and they never target common people unless…"
Jin froze.
He realized he had already been marked by the strongest forces in this world.
He liked fighting strong opponents—but not ones who could kill him instantly.
He needed to know why he was being targeted. But first, he had to ask about the Demon Moons—after all, someone like him shouldn't already know about them.
"Demon Moons?"
"Oh! I forgot to explain. The strongest demons are known as the thirty Demon Moons, servants of Kibutsuji Muzan—the progenitor of demons and the King of Demons, who has walked this earth for over a thousand years."
'Thirty Demon Moons…'
'This world is doomed.'
Jin's face fell, but Rengoku continued.
"They are divided into upper and lower ranks, fifteen each. The one who attacked your family was Lower Moon Rank One. In other words, the seventeenth strongest demon in the world."
Jin fell silent.
Rengoku sighed.
"Your family is not the only case. This happens every ten to twenty years. After analyzing the pattern, we concluded that there is a demon capable of predicting the future. That demon informs Muzan about potential threats."
Jin snapped out of his daze and began thinking.
"I have a question."
"Ask."
"Do demons always kill every member of the family, or only specific individuals?"
"They kill every member. Even those living in different countries are hunted down—without exception."
'Thank God… I'm safe.'
'The original Jin is already dead… as long as I don't reveal my real identity.'
"Rengoku-san, I have a request."
"Go on, young Jin."
"Please keep my identity a secret. And… register my name as 'Mitaka Jin.'"
"Very well. I will keep your secret from everyone except the Master. And rest assured—given your talent, you may be able to contend with Demon Moons within two to three years."
"I understand."
"Now, I must take my leave. Don't forget to report to the training hall tomorrow morning."
With that, Rengoku disappeared.
Jin stood there for a while, lost in thought, until he felt a tap on his shoulder. He turned to see Gotou.
"Hey kid, come back to reality and follow me. I'll show you where you'll be staying during your training."
"Okay."
Next Day
Jin stood in front of the training hall, wearing a trainee uniform—a grey buttoned shirt, grey hakama pants, and sandals.
After a brief hesitation, he stepped inside.
Nine other cadets stood in a line before a podium. Jin joined them, standing beside a brown-haired boy who looked about fifteen.
The atmosphere was tense.
No one spoke.
Suddenly—
The podium burst into flames, revealing Rengoku's silhouette, his fiery eyes gleaming, and a faint smile on his face.
'Yesterday I was too overwhelmed to notice… but he looks so young… around sixteen or seventeen.'
"Rengoku-sama!"
Everyone except Jin knelt.
'What am I supposed to do?'
Noticing his awkwardness, Rengoku signaled everyone to stand and begin training.
The cadets quickly split into groups to spar. Meanwhile, Rengoku approached Jin, who stood alone in a corner.
"Rengoku-san…"
"You don't need to feel awkward. They've been here for a while and already know the basics—that's why I separated you."
"Sit down and practice Concentrated Breathing until you can feel the energy flowing into your body."
Jin received a manual and began reading. Within minutes, he grasped the concept—it was surprisingly simple.
"Now, take that sword and begin swinging it while maintaining Concentrated Breathing."
Jin picked up a sword and started swinging.
*Slap
"Achk!"
He opened his eyes to find Rengoku crouching in front of him, pressing his abdomen.
"Put more strength into your core."
Jin resumed his swings. Rengoku occasionally struck his abdomen to correct his form.
After some time, Jin began to feel a faint flow of energy circulating within him—far weaker than what he had felt in battle, but unmistakable.
"Rengoku-san, I can feel the energy. What should I do next?"
Rengoku, who had been instructing another cadet, turned with a surprised expression before smiling.
"Now, try to move that energy throughout your body at will while continuing your swings. It will gradually temper your entire body. Once you can control it freely, I will teach you the forms of Flame Breathing."
Jin continued training.
After a few hours, he realized—
He could already control the energy completely.
Across the hall, Rengoku watched him, beads of sweat forming on his forehead.
'What a monster…'
'He's doing in hours what even geniuses take weeks to achieve…'
'I just hope he can create his own breathing style… only then will he have a chance to stand among the Pillars.'