When Yu IlHan cleared the first round of aerial monsters from Earth using the flying fortress, Earth finally caught a glimpse of a clear sky without a single monster after the Great Cataclysm. This happened merely 4 days after the flying fortress took to the air.
"Though, from the look of things, it would go back to usual after one week at most."
[Let's not talk about something so power-draining when you just achieved something incredible.]
"Why? It's much better for monsters to be re-supplied periodically rather than having them disappear all of a sudden."
[I get that killing monsters is the same as grilling meat to you…]
Of course, since the flying fortress was treated as Yu IlHan's equipment, if he didn't want to encounter monsters, he should just keep it concealed and fly around the sky, but he didn't. There was the flying fortress, and there were monsters. What reason was there to hesitate?
"Then let's go over to another country. Let's start from Japan, which is the closest, and do a trip around the world."
[That's nostalgic. Last time, we went to China first.]
"There were limitations in the means of transport back then, but now-"
[Ah, I get it. I get it so you don't have to explain the A to Z on the flying fortress.]
Just as Yu IlHan was about to lecture Liera about his masterpiece for 3 hours straight, she stopped him. So, Yu IlHan skipped the basic explanation and went on to explain the plan's specific details.
"Then after I am sure that I've cleaned up all the countries, then I'll start cleaning up the seas. After cleaning up the whole Earth like that….."
[You're going to start training alone?]
"Training can be done by hunting monsters. At that time, aerial monsters will start spawning again. And after I clean them up, quite a lot of monsters would have appeared on the ground….."
[...]
Liera thought hard after hearing that. Perhaps Yu IlHan's words about replacing the 7 billion humans were no joke, but rather a conclusion drawn from meticulous calculation!
And his plan really did go successfully.
The flying fortress was designed to handle any situation, so even if the monsters spawning on Earth were freaks born 4th-class, it could handle hundreds of them simultaneously.
[You have...]
[You have...]
[You have...]
Wherever the flying fortress went, Yu IlHan ruled. Whether it was the skies, lands, or seas, nothing could stop his advance.
The Hundred Eyes recharged their energy using the mana from the monsters they killed, and those that could endure even that were taken out by Yu IlHan's surprise attack. Yu IlHan didn't like this so much.
"They're too weak compared to the ones in the hell dungeon."
[So you're already used to the horrible nature of those things…..]
"Hm, I wonder if there won't be any natural-born 5th classes?"
[I said that you need to be in a faction to become a higher existence. You really don't listen.]
Of course, Liera thought it was very likely that a natural birth of a 5th class would occur on Earth, but didn't say that out loud. She was afraid her thoughts would be found out by him.
And while she was not saying anything, Yu IlHan had ended up coming up with a horrifying plan.
"This won't do. I think I need to reduce the output of Hundred Eyes to train my skills."
[Turn it off!? Are you crazy?]
"Not completely. To reduce the consumption of mana, I have a power-saving mode that utilizes only 20 of them and blocks only the most fatal attacks."
[Power-saving mode!? ... Well, yeah. It can be charged and even has a vibration mode. There's no way it does not have a power-saving mode. Urrgh…..]
Liera was in the realm of emptiness that had given up everything. Even if she wasn't an angel, perhaps another path would have opened for her as a higher being.
[Kuhaaaaaaah!]
[The mana disappeared! The damn mirrors are gone!]
[Everyone charge! Let's rip apart the hated human and dry his corpse out!]
When the Hundred Eyes' movements grew a little dull, the monsters all charged forward as if they had been waiting for that moment. No matter how smart monsters were, they were still monsters! The other weapons stationed around the fortress finally had their turn, and Yu IlHan could hone his skills to his heart's content as he rampaged.
"Give me thought-souls!"
[Kyaoooooh!]
The skills he had to master to become 4th class were: Deathgod, Blaze, Soul enchant, Death collector, Transcendent regeneration, Extreme poison resistance, and Higher curse resistance; a total of 7.
With the blessing of the goddess of fire, he would finally be able to advance to Hell Bringer, but that wasn't something he could do anything about, so, leaving that aside, he decided to master what he had first. Of course, the target of training was Earth itself. It was a larger scale than anyone could try!
However, it wasn't only Yu IlHan that tried his best.
[Give me more thought-souls. To defeat those damned freak demons inside master's consciousness, I need to become stronger!]
"Yes, yes. Eat all of them! If you achieved 177 losses out of 177 battles today, it's your victory if you gain even one victory tomorrow, Orochi!"
[Ugh, how the hell do you know how many times I've lost!]
Of the characteristics of Yu IlHan's class, Soul enchant and Death collector, which belonged to the Deathgod skills, were harder to level up than most others, but with his loyal thought-soul Orochi, it was not that hard.
Death collector grew the more he acquired thought-souls and raised them, and Soul enchant gave him experience whenever he forced a strong thought-soul to submit and enchanted it.
Seeing Orochi trying his best without even needing to be urged, these two skills looked like they would be mastered soon without having to worry too much about them.
There were no problems with the Deathgod skill, an advanced version of Concealment, or the Blaze skill, which emphasized his trait as a Blazing Reaper, since they would grow with frequent use.
Although skill levels became harder to increase through training the higher they rose, the enemies he was facing were 4th class; they were all 1 class above him! There was no way his skill proficiencies would not rise when facing such enemies.
Of course, compared to the freak demons in the hell dungeon, the level of monsters on Earth was much lower. However, the monsters of Earth propagated at speeds that rivalled those of cockroaches, so they could cover that gap in numbers.
Transcendent regeneration? That was the easiest to level up. Ever since Earth came to this state, there have been monsters with even more monstrous regenerative capabilities than trolls, and Yu IlHan could replenish his rest energy by making new-bloodrink from their blood.
Now that he was in a situation where he could use that skill infinitely, the only thing left was getting hurt in order to recover, and this could easily be countered by using the master-level Superhuman strength.
"Hhp, Hhhhhhhp."
Seeing Yu IlHan actually carrying out such an absurd plan, Liera muttered in shock.
[Would there be anyone who would use Superhuman strength in order to get hurt? Oh, wait. There are no humans with such a skill set in the first place.]
"Hhp!"
To mention it again, the skill Superhuman Strength was originally not something a human could learn! This was a skill that the angels could acquire after scraping out the records of the monsters absorbed into Yu IlHan's body, as Yu IlHan's records, achievements, and actions on Earth were too amazing.
It was insane that he had mastered such a skill, but Yu IlHan was using it to its full potential to destroy not only his bones but also his internal organs, only to regenerate them instantly with the Transcendent regeneration skill. He was undergoing such an insane training method!
"Hhp... Even so, it's good because my abilities are increasing in real time. Whew, I can swing around tens of thousands of tons!"
[You might blow the mansion away! ....And doesn't it hurt?]
"It hurts like hell. Do you have to ask?"
Said Yu IlHan seriously. Well, even in Liera's eyes, he looked to be in pain. Yu IlHan wouldn't usually sweat much, but right now, he was sweating blood all over his body.
Moreover, when she listened closely, she heard faint crunching sounds amid the monsters' roars and Yu IlHan's own shouts. Liera shivered just thinking about the source of that sound.
[...And you're enduring that? Experiencing muscles being torn and bones breaking at every single moment?]
"If I don't feel pain here, then I'll feel even more pain later, so I need to endure. Physical pain that does not lead to death can be endured; it is nothing compared to psychological pain."
[Sheesh, that's why I'm saying you're not human. Although, I like you because of that!]
"I also like myself because of that! Hhp!"
The pain of loneliness, the pain of being unable to protect, the pain of having to let go despite the scene right before his eyes. Yu IlHan shall not face such pains again. And to do that, he needed to suffer pain right now.
Of course, the fruits of such intense labour were sweet. With his muscles constantly enhanced to an extreme, he was now able to do things that ordinary lower existences wouldn't even dare try!
"Huaaaaaaap!"
[...Little Giant should have been quite a sight to look at.] Liera muttered while looking at Yu IlHan swinging the hammer. Well, that was no wonder, since this 'hammer' was a city-destroyer-grade hammer with a 20m-diameter head and a 30m-long handle. It was destroying all the monsters at the front with sheer muscular power.
Of course, nothing remained in the aftermath of the hammer.
"I'm done cleaning!"
[This is not a house we're talking about!]
"Damned things. They're coming at me like middle schoolers to the cafeteria at lunch."
[So IlHan also had such a cute time?]
"Of course, I was reading a book in the classroom while no one was there. Thinking about how a girl tried to sit on top of me, thinking that I really wasn't there, is quite a good memory if I think about it now."
[....]
Seeing monsters flood into the blank area he had just created, Yu IlHan gripped the hammer's handle and began spinning it, pouring an enormous amount of strength into his arms. As the hammer spun faster, with him as the axis, the monsters were ripped apart by the wave alone!
[Kihi!?]
[Kuaaaaaaak!]
He was using the floating Aegis as the foothold to spin endlessly! With Blaze added on top of that, a storm of fire appeared in the region. Whether they jumped into the fire or were hit by the spinning hammer, they would see hell.
What was scary was that the Aegis was moving the storm of fire at will!
"Let's go, Hell Tornado!"
[Crap name!]
The hammer he was swinging around right now was none other than the Thunderhammer. After he had mastered the Superhuman strength skill, he switched the materials to increase the weight and size by 10 times, so he could use his increased strength! Of course, the hammer was reborn as an epic-rank weapon.
[The skill, Deathgod...]
[The skill, Blaze….]
[The skill, Transcendent regeneration...]
The more Yu IlHan rampaged on the stage known as the flying fortress, the more he realized the limits of his abilities and values, and the faster his skills rose in level. Accordingly, the master-realm of many skills that he estimated would take several years to master was nearing mastery as of this moment.
However, not all of his skill training was smooth.
[You have earned 3,124,335,618 experience.]
[You have earned the record of Lv 233 Wicked Kraken.]
"God dammit."
Yu IlHan just killed an enormous kraken over 300m tall and erased all the kraken-ink covering its body with Blaze, after which he cussed.
"This guy's poison is too weak, too."
[The curse was at a pitiful level too. Strangely, monsters around here have weaker poison and curses compared to their power levels. It's as if they were all sucked into somewhere.]
"So it's that guy." Yu IlHan muttered in resentment. In fact, Yu IlHan also knew without having Liera tell him about it.
There was no need to discuss this. The dungeon he was trapped in the past for 2 years! The master of that place had put all the poisonous and cursed monsters in there. Definitely.
"Did you really have to take everything?"
[Though, that guy wouldn't have done that to tease you either.]
"I don't care about the truth! What's important is that this is the fault of that bastard son of a bitch.'
[Yup, I knew you'd say that.] As Liera sighed, Yu IlHan abruptly raised his head, his eyes glistening.
"Now that it came to this, I can only use the final method."
[....That sounds VERY ominous.]
Muttered Liera. However, Yu IlHan ignored her and unfolded Ruin Calling, leaping out of the water. The place he was heading to was none other than the flying fortress. His answer lay there.
His battle had just begun.