I Became the Mentor of the Weakest Demon King

Chapter 64



Chapter 64

Upon returning from the human world, Dein immediately headed to the 56th floor at Nahun’s command. Using the portal to the demon world personally was easy as long as he disguised his identity.

“I made it to the 56th floor somehow.”

Nahun had created a fake identity for Dein through his connections with Bernet, allowing him to swiftly reach the 56th floor. However, as soon as Dein set foot in the portal and arrived at the 56th floor, he felt a sense of confusion.

“…What’s going on?”

He had clearly heard that a war had broken out, yet the scenery of the 56th floor was utterly peaceful. Thinking it might be because it was the outer region where the portal was located, Dein quickly made his way towards the vicinity of the Demon King Castle, utilizing his dexterous thief skills.

But the area near the Demon King Castle was also oddly calm and tranquil. Finding it strange, Dein cautiously asked a passerby.

“Excuse me, may I ask you something?”

“Go ahead.”

“Was there a war on the 56th floor? I heard something about that while I was making my way up, so I came with a bit of anxiety, but it seems like no war has occurred at all.”

“Oh, that? Lord Gremony didn’t touch the city or the civilians at all.”

“…Huh?”

Dein tilted his head. How could such a thing happen in a war? Even if they managed to control not hurting civilians, it made no sense to fight a war without affecting the city at all.

“There was a war, wasn’t there? That doesn’t make sense…”

“Oh, that. Actually, the war wasn’t really warlike. It’s true that they descended with an army from the 55th floor, but before they could truly clash, Ose, who was ruling the 56th floor, was assassinated.”

“Assassinated?”

By whom? Before Dein could ask for further details, the man provided an answer.

“It’s rumored that one of Ose’s subordinates betrayed him and caused the assassination.”

“Any idea why?”

“I don’t know the reason well. Perhaps it’s because they didn’t like Ose’s rule?”

“…Thank you for the information.”

Thinking he should gather a bit more information about this rumor before reporting back to Nahun, Dein slowly took his leave, and the passerby watched him disappear for a while.

Shortly after Dein left, a man approached the passerby.

“Did you catch any bait?”

“Yes, it seems like a spy from Seere von Debata. Just as you said, they conveyed the story. But something felt off.”

“What do you mean?”

“It doesn’t seem like they’re a demon. I couldn’t feel any magic power from them.”

“…Are you saying you used a human as a spy?”

“I believe that’s possible. You know that Debata dealt in human slaves, right?”

The passerby looked at the man. The black-haired man slowly stroked his chin and simply said.

“…We’ve gained a pawn.”

“Eh?”

“No, it’s fine as long as they did well as instructed. Return now.”

“Yes, General.”

The soldier disguised as the man and the passerby left the area. The gaze that had been watching them from a nearby alley also vanished. The man who withdrew his gaze quickly exited the alley, muttering to himself.

“Did they notice that I’m human…?”

It was Dein. He had pretended to leave, hiding himself to monitor the passerby instead.

The overly kind explanation from the passerby for someone he casually encountered, along with knowing that the Demon King had been assassinated just days after the 55th floor conquered the 56th, felt off. Gremony hadn’t publicly declared it either; if they had, the information would have already spread.

And sure enough, the identity of the passerby was someone from the 55th floor. Dein pondered for a moment and resolved to relay this information directly to Nahun.

The information conveyed by the soldier from the 55th floor was certainly factual. The deliberate approach of contacting him and the detailed explanation were very transparent in intent. It was evident that there was a desire to pass this information along to the Seere side.

“I don’t know their reasons or intentions, but…”

That wasn’t a matter for him to judge. Thinking that, Dein took one last look around before heading back to the 69th floor.

#

From early in the morning, Nahun and Seere were at the training ground. Nahun hadn’t chosen this place for the lesson; it was at Seere’s request.

Seere was holding the blood loop sword, while Nahun had a basic iron sword.

“Teacher.”

“Yeah?”

“If I win, you’ll answer my question, right?”

“…What kind of question could be worth a duel?”

To Nahun’s surprise, Seere smiled brightly and said.

“It’s a secret!”

With that short phrase, Seere dashed forward. Taken aback by the sudden start, Nahun exclaimed.

“Are we starting!?”

“Of course!”

Clang!!!

However, considering he was startled, Nahun managed to successfully block Seere’s sword strike with great skill. Seere let out an exasperated breath and slightly empowered his blade to push him back, creating distance.

“Tch, I was aiming for your opening.”

“When did I say we could start? You surprised me.”

“You were defending incredibly well for someone who was surprised!”

The clash of their swords filled the training ground with metallic sounds. Seere swung his sword rapidly, trying to apply pressure on Nahun, but Nahun didn’t allow even a single attack to succeed.

‘I can’t see any openings…!’

Seere was putting forth all his strength. Determined to strike Nahun in this duel, he was giving it his all. To exaggerate, it was like he was facing Belial; he was fully committed.

But Nahun, armed with only a basic iron sword, effortlessly deflected or parried every one of Seere’s attacks. He was completely absorbing and redirecting them. He wasn’t dodging at all.

In fact, aside from a few steps taken to adjust his footing, Nahun hardly moved from his initial position.

“Ugh…!”

Seeing no openings at all, Seere was slightly irritated and stomped the ground again. This time, he gripped the handle with both hands and struck down with all his might.

Boom!

“Using too much strength isn’t good either, Seere.”

“Gah…!”

Even though he poured every ounce of effort into that strike, Nahun blocked it head-on with his arm, showing no sign of trembling. It demonstrated just how little effort it took him.

“And when you fight, you must always remain calm. Emotions cloud your judgment.”

“…!”

As Nahun swung his sword upward in a circular motion, Seere’s sword was sent flying into the air.

“Ah…!”

Clang!!

Nahun sent Seere’s sword flying far away. The blood loop sword soared into the sky, rotating about three times before embedding itself into the ground of the training ground.

“I suppose I won.”

“…That’s cheating!”

“Hmm?”

“Teacher, you don’t give any openings at all! It feels worse than Lin!”

Seere complained, saying it was unfair. Nahun scratched his cheek at his cute student’s grievances. He was merely moving based on memories that rose to the surface and what his body instinctively remembered. Yet to hear Seere say it was worse than Lin was surprising.

‘…Is it because of my demon lord body?’

As a being of a great demon, Nahun was aware that his body wasn’t ordinary. But when he occasionally experienced it like this, it felt both fascinating and surreal.

Seeing Seere still pouting with her lips protruding, Nahun chuckled softly. He sheathed his sword and approached Seere, raising his hand.

“It’s fine.”

He gently cupped Seere’s soft cheeks. As her chubby cheeks squished softly, Nahun felt an inexplicable wave of joy.

“Surely the day will come when you become stronger than me. No need to rush. You’re only twelve, after all. Reaching this level is already something impressive.”

“…….”

There’s no need to rush. Seere usually accepted and embraced whatever Nahun said, but this one thing she couldn’t acknowledge.

“…I want to get stronger quickly.”

“Right, I understand your feelings. But the more you rush, the more stress you’ll feel, and things won’t go as smoothly. So take your time.”

Nahun slightly curled the corners of his mouth. Speaking almost like a plea, he cautiously shared advice born out of experience.

“I hope you don’t become someone who’s too fixated on outcomes. If you do, your heart will become worn down.”

Seere tried to say something but ended up closing her mouth. Internally, she was greatly shocked. She couldn’t express it outwardly for fear that Nahun would view her strangely.

‘Why…’

Nahun’s smile looked strangely sad. As she confirmed his expression, Seere gently nodded.

“…Yes.”

“Alright, as long as you understand.”

Nahun withdrew his voice. Then Seere spoke.

“Teacher.”

“Hmm?”

“I’ll listen to everything you say, Teacher. So…”

Seere gazed at Nahun. Nahun couldn’t help but flinch at the look in her eyes. Her eyes, resembling the blue moon of the demon world, had a hint of sorrow.

“Please don’t be sad.”

“…….”

Nahun couldn’t utter a word. He hesitated for a moment and pressed a hand to his forehead, feeling self-reproach.

‘What am I doing…?’

He revealed unnecessary emotions. Yet, whenever he looked at Seere, it reminded him of something he had missed in the past. Still, there had been no need to make this child worry—this was a significant mistake as an adult, before being a teacher.

Nahun sincerely apologized.

“I’m sorry, Seere. It’s not because of you.”

“…Really?”

“Of course. You bring me joy; why would I be sad looking at you?”

Nahun said that, gently patting Seere’s head. As Seere’s apologetic expression eased, Nahun found himself satisfied, smiling subtly.

“Am I really your joy?”

“Of course. There’s nothing more joyful than seeing you grow up so wonderfully and become stronger.”

“Hehe…”

Seeing Seere’s delight, Nahun couldn’t help but chuckle. Then, playfully, he spoke.

“But your curiosity will have to wait for the next time. Since I won, right?”

“Ah…!”

Seere’s mouth opened slightly, and she slumped in defeat. Nahun lightly laughed and looked up at the training ground. A man had been waiting there until their duel concluded. Nahun spoke to Seere.

“Let’s end the duel for now.”

“Did you call him? I wondered why he was lingering around.”

“Yeah. I needed to check something. I’ll just have a brief talk and come back, so practice on your own for now.”

“Yes, Teacher.”

Nahun set his sword, sheathed, in the storage and climbed the stairs to the training ground. He then spoke to Dein, who had been waiting for a little while.

“Did you find out?”

“Yes, Nahun-nim.”

“What’s the situation?”

“First of all, the 56th floor is intact.”

“It’s intact?”

How could a floor that had just undergone a war, a unilateral invasion at that, be intact? As Nahun cocked his head, Dein reported all the information he had gathered without missing a beat.

“…So they intentionally leaked that information?”

“Yes, it was very suspicious, so I decided to investigate undercover, and I ended up speaking with the general you mentioned from the 55th floor.”

Nahun had given Dein basic information about the forces of the 55th floor and had him do some reconnaissance. The fact that one of those people was involved meant…

“Who was it?”

“I’m not certain from this distance, but I noticed they had black hair…”

“Is it Blackstorm Vitos?”

“Yes.”

Blackstorm Vitos was a general under the demon king Gremony von Due of the 55th floor. Due to the size of Gremony’s forces, there were several individuals holding the title of general, but the three most famous ones were referred to as the ‘Three Stellar Generals.’

Since Vitos was one of those Stellar Generals, the information Dein provided was highly likely to be true, which meant that the 55th floor had intentionally leaked information to this side.

As Nahun pondered the reason behind it, he narrowed his eyes.

“…Are they trying to establish an alliance?”

“Eh?”

“The fact that they intentionally leaked information means they wanted you to relay that information to us. But our impressions of the information you provided will likely be…”

Nahun raised his index and middle fingers as he spoke.

“First, the perception of the 55th floor’s lord, Gremony, among the inhabitants of the demon world is relatively positive.”

“Yes.”

“And the 55th floor is not only strong in power but also adept at manipulation and stratagems.”

“Indeed….”

“It is highly probable that the claim of Ose having been assassinated is true. To either kill a ruling demon king or have them surrender directly without touching the city at all is impossible. Moreover, the assassination had a high likelihood of being orchestrated by the 55th floor from the start. The sudden betrayal of Ose’s subordinate feels too staged.”

Ose wasn’t a weak demon king, nor was he someone with problematic character leading to numerous enemies, or a ruler with significant governance issues.

It was clearly the 55th floor’s machinations. The claim that Ose was killed by a betrayal from his subordinate was less an excuse to conceal the truth and more an excuse begging one to notice. The intent was clear…

“They’re trying to appeal to us.”

“Are they suggesting we form an alliance with them?”

“The fact they specifically targeted and disseminated information to you carries a strong intent. But…”

The purpose of the alliance was murky. For a demon king of the 55th floor, there would be many tiers willing to accept alliance requests without difficulty, given there were demon kings much more powerful than them. There wasn’t a need to align specifically with Seere von Debata.

‘Is it because Seere defeated Belial?’

Given Belial’s strength, this seemed like the most plausible explanation.

“What will you do?”

“Well, it’s not a bad idea. Having the 55th floor as an ally would certainly be beneficial, but…”

The fact that they were adept at manipulation and scheming put Nahun on edge. If they were to unwittingly ally with them and get backstabbed, having their accumulated effort handed over to Gremony…

“…Dein.”

“Yes?”

“Keep monitoring the dynamics of the 55th floor. Also, don’t engage with anyone else, and this time, travel in disguise.”

“Understood.”

Dein nodded slightly and then glanced at Nahun with a hint of worry in his expression.

“Nahun-nim.”

“What’s wrong?”

“Eri is…”

“Eri will remain in the human world. You know that as well.”

“…I understand that. What I wanted to mention wasn’t that…”

Nahun tilted his head momentarily before realizing Dein’s expression was inherently anxious, understanding his thoughts. He spoke reassuringly.

“If anything happens to Eri, I’ll let you know immediately, so don’t worry.”

“…Thank you.”

“You’re still valuing your friend.”

“Of course.”

Dein held his head up high, and the determination was evident in his steady gaze directed at Nahun.

“Because she’s my last remaining friend.”

“…Is that so?”

Nahun nodded. Remembering their deceased friend from five years ago, he gently closed his eyes. It was necessary to brainwash humans and send them as spies. The operations conducted through that process ensured Seere von Debata’s faction secured abundant funding.

It had merely been a coincidence that the candidate for the hero had gotten involved, and Nahun hadn’t even known that Luke had been captured. It was all mere coincidence that the hero candidate, Luke, had been turned into a spy and then killed.

Yet, as he learned more about Dein and Eri, Nahun felt a twinge of guilt. After all, it was because of his command that Luke was brainwashed and set into motion.

Thus, he wished for Dein and Eri to live well. Initially, it had been to derive practical purposes from them, but now there was also a sprinkle of goodwill.

“Dein.”

“Yes?”

“If it makes you that happy, taking her as a wife to keep her close wouldn’t be a bad idea.”

“…!?”

Dein’s face went stiff in shock, prompting Nahun to look at him inquiringly.

“I thought it was a good idea. Generally, don’t humans live their lives having one partner for life?”

“That may be true, but Nahun-nim…we’re not in that type of relationship. My fondness and care for Eri is purely as friends; it doesn’t mean….”

“I know it’s not that way. I’m just speaking realistically. You and Eri are the only humans living relatively freely in this vast demon world.”

Nahun spoke plainly.

“It was merely a suggestion to think about. Don’t take it too heavily; don’t make that serious expression.”

“Ah… I’m sorry.”

“You should continue monitoring the 55th floor’s movements until I summon you back. Go now.”

“…Yes.”

Dein nodded and then stepped back, leaving. Nahun sighed after confirming he had left. He scratched his head slightly and murmured.

“Was that unnecessary meddling?”

“…Teacher.”

“Hmm?”

At some point, Seere had come up the training ground stairs. He hadn’t even noticed when she arrived. Nahun blinked and asked Seere.

“Didn’t you complete your personal training?”

“I did everything. So I came up, but it seemed you were still in the middle of a conversation, so I waited.”

“Oh, is that so?”

“But, Teacher, what do you mean by suggesting I take a wife?”

Nahun felt a bit odd. Seere’s gaze directed at him… something felt off. It was as though she was exuding sticky emotions; he had never seen that look in her eyes before.

Nahun tightly closed his eyes, reopened them, and noticed that the eerie look had vanished. Only the pure gaze of a child remained.

Clearing his throat, he regained composure and spoke.

“Ah, it seems you overheard? That was advice I offered to Dein.”

“Dein? That human is taking a wife?”

“It’s not exactly that….”

Nahun briefly explained to Seere. She then tilted her head in contemplation.

“Wife and husband refer to those who are married, right? So… marriage.”

“Exactly.”

“What changes with that?”

“Responsibility emerges. Married couples have a responsibility to protect their household and stay by each other’s side. I mentioned it because it seems Dein worries about being away from Eri.”

“Ah… then do you feel that way as well, Teacher?”

“Hmm?”

“You know, responsibility.”

Why did my story suddenly turn to myself, Nahun wondered. Still, since it was Seere’s question, he felt the need to answer it. He contemplated for a moment and nodded.

“Isn’t it inevitable that it would develop? It seems it’s only natural.”

“…I see.”

Suddenly, Seere bent her head and turned to leave briskly. Nahun stared at her departing figure in bewilderment and tilted his head.

“What was that about?”

Has she suddenly entered a phase of adolescence?

#

Seere quickly returned to her room. She opened her notebook and started writing something fiercely with a pen. After some earnest scribbling, Seere set the pen down and muttered.

“Couples must protect their household and remain by each other’s side…”

She was reflecting on what Nahun had mentioned a moment ago. At the very top line of Seere’s notebook, something was written.

[How to ensure the Teacher doesn’t leave.]

Below that, there was a crossed out section, barely visible, with just a few characters legible…

[Teacher, forced, external magic, ….]

In stark contrast, the newly written content was displayed clearly.

[Marry the Teacher.]



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