The next day, Sukuna followed the path Erde told him about and arrived before a large opening in the ground.
Due to his demon lineage, he was able to see perfectly well in a dark environment.
Entering the cave, Sukuna started exploring it.
His figure moved at quick speed, traversing the rough, uneven ground with great flexibility.
As he was going forth, he noticed the ground under his feet started changing, becoming more even.
Not long after, he appeared before a large metal door, embedded with green gems.
'Forget the treasure, I'm taking this door.' Sukuna's eyes glowed with wonder at the intricate markings present on it.
Walking up to it, he touched the door, making the gems light up before it parted open at a slow speed.
Looking inside, he saw a whole passage made of large solid bricks.
Running through the passage, he encountered some worm-like monsters spitting acid from their mouths.
Under his magic technique, the worms were split apart, splashing burning acid all over the place, making Sukuna frown.
'What a troublesome monster.'
After stepping on the few places not covered in acid, he continued forth and arrived before a small opening on the side.
Looking inside, he saw a large chest made up of wood and iron on the edges.
'It's not a mimic, is it?'
Sukuna wondered in curiosity as he sent a slash at the corner of the chest.
As soon as his slash split off a part of the chest, the chest opened up, revealing a large mouth filled with teeth
'Damn, no treasure here.'
Sukuna sliced the mimic up into small blocks before continuing his journey through the passage.
During the journey, he encountered several different large and small monsters, but they were no match for his slash attacks and would die almost instantly.
Finally, after killing his nth monster, Sukuna found a normal chest.
Opening it up, he quickly looked inside with excited eyes.
There were two ancient-looking books as well as a silver-blue staff and a bronze helmet.
He curiously tried out the staff and found that it made casting his magic a little smoother.
Though the difference really wasn't that great to have much of an effect.
Still, it was a hit loot.
Picking up the entire chest, Sukuna placed it inside the passage and then continued onwards.
He will take the chest back with him while returning.
After a few more skirmishes, he suddenly found a large open gate in front.
Walking inside, his eyes witnessed an extremely large space, surrounded by random pillars here and there.
And at the center of those pillars was a large golem.
'Boss monster?'
Sukuna thought in his mind as he entered the room, instantly attracting the large stone golem's attention.
*Boom*
The golem's large fist hit the ground, cracking it open.
Sukuna casually jumped away and arrived beside the golem and placed his hand on it.
And almost instantly, countless slashes were released by him, breaking through the golem's stone body, making it stumble and fall back on the ground.
Sukuna didn't give it a chance to recover and continued sending slashes until the monster was completely broken into pieces.
From the rubble of the golem, he picked out a hand-sized, round sphere that emitted magic.
'Something like a magic core?'
Sukuna took it with him, then walked up to the middle of the room, where a chest lay in silence.
Opening it up, Sukuna found another book, along with a bronze-colored full body armor, bronze shoes, and a glowing silver warhammer.
'A war hammer?'
Sukuna looked at the unconventional weapon with interest.
Holding it with one hand, he swung it around for fun before crashing it on the ground, cracking it open.
Even after the rough attack, the hammer remained unaffected, boasting its powerful craftsmanship.
'4 grimoires, a bronze armor set, along with a powerful war hammer. '
That's all this dungeon had to offer.
Sukuna placed everything back in the chest, then picked it up and rushed back, picking up the other chest on the way before exiting the dungeon.
Looking at the setting sun in the distance, he didn't waste any time and quickly rushed back home.
There, he dug up the ground and threw the chests inside before rushing back to the dungeon.
Looking at the large metal door as well as the perfectly shaped light yellow blocks of the passage, he made up his mind and got to work.
After running to the end of the tunnel, he carefully used his magic to cut the blocks before pulling them out.
He knew about the risk of the cave falling on him after losing support, so he made sure to start from the end of the passage, not the front.
This way, even if the cave fell, the main passage wouldn't be affected.
Then throughout the entire night, he repeated the process, removing blocks and taking them to the entrance before going back and removing blocks again.
Though the place was too large, he only managed to finish a twentieth of the path in a whole night while working nonstop.
Fortunately his mana reserves were huge, plus the recovery rate was also quite crazy.
With some hard work and dedication, within a month he was able to retrieve every single useful block from the dungeon and bring it to the surface, near his log house.
The villagers questioned what he was going to do with all of them, to which he replied he was still thinking about it.
Lying on his bed, Sukuna silently read through all four grimoires.
There was a spell that gathered water from the air.
A spell that makes a temporary floating light orb to act as a light source.
A spell that cleaned dishes.
And finally... a spell that controlled earth.
Sukuna quickly learned how to use all of them; he focused especially on the spell that controlled the earth.
Waving his hand, he used the spell, making a sharp spike suddenly come out from the earth and pierce through a nearby tree.
It was a very useful spell, but it had a major restriction.
As long as the piece of ground is disconnected from the earth, his magic will lose its effect, and he will be unable to control it.
Meaning he can change the terrain but cannot make a piece of land float into the air.
This spell was so useful he couldn't believe he found it in a random dungeon.
He could do so many things with it... like build a whole kingdom...
Sukuna trembled with excitement just thinking about it.
'Since I am here... I might as well try it...'
Using his memory of the surrounding area, he quickly made a mind map.
'I have to make it near the sea... it could actually be a port town in the future...'
Due to its unfriendly and treacherous terrain, a working city was never built in the Gran plain.
Since, although it was connected with the ocean, the Rocky Mountains and shallow water near the edges made it unsuitable for such endeavors.
Plus they had a more suitable location down south, so the human kingdom just built a port town there instead of on these unfavourable terrain.
But he, Sukuna, with his large mana reserves, can change all of that.
'If I have the villagers move in too, it can totally work as a town...'
A city of humans built by a demon.
It sounded kind of fun.
The next day, he approached the villagers and explained his grand plan to them.
They were clearly dumbfounded by his words, but when he used his magic to create a small mountain in the distance, they quickly fell silent and started thinking about the feasibility of the plan.
Sitting together with the builders of the village, Sukuna started building a plan of action.
It was a long process.
He first visited the entire area connected with the ocean, checked for the nearby roads leading to the kingdom, and several other things.
Several sketches were made, several plans were changed, and some were discarded entirely before they arrived at one that seemed feasible.
Still, there were several issues they, as simple farmers and a demon without much construction knowledge, were unable to solve.
So they made a decision to visit the nearby city of Warm, which was a trading port, which they could learn a lot from and even consult an architect there.
Though the problem was...
"Mr. Sukuna... It will be hard for you to enter the city...."
It was a given, especially since humans and demons were currently at war.
The best thing will be for the villagers to go there by themselves.
'But I want to learn human magic...'
According to the story, humans will progress their magic rapidly in the coming years.
It will be a good idea to learn from them if he doesn't want to be left behind.
'Alright, I'll sneak in.'
So, with four other men, Sukuna left the village on a carriage, making his way towards the port town.
"Steve, how long will it take for us to reach the town on the carriage?" Sukuna asked, looking at the weak-looking donkey pulling their cart.
"Hm? About a day, I believe? My donkey will need to rest since he gets tired easily..."
"...."
".....You know what, pull the donkey on the cart; I'll carry you all there."
"B-but Mr. Sukuna, won't you get tired?..."
"Just do it; it's faster. Also, I can't sit on this hard wooden seat for a whole day."
And so, Sukuna picked up the carriage and then carried all of them, including the donkey, across the road at quick speed.
Due to his monstrous mana and stamina, the journey was covered in less than 2 hours.
"Mr. Sukuna, you're really amazing...."
The village men muttered in awe, staring at the city wall in the distance.
Sukuna also blinked in curiosity at the medieval structure.
They were currently in a discreet spot to avoid exposing his demon identity.
"Mr. Sukuna... they have guards at the gate..."
"It seems they are checking everyone...."
Sukuna looked at the castle walls and saw guards stationed on them.
It seems climbing the wall wasn't an option.
'Since it is a port city, maybe I can sneak in from the sea—no, wait, what is that...'
Sukuna's eyes narrowed as he suddenly sensed something wrong and expanded his senses towards the city.
It was then that he noticed a peculiar detail.
'A barrier?'
There was a barrier surrounding the port city.
He suddenly remembered that in the series, several major cities had barriers protecting them to keep the monsters and demons out.
'But I'm also a demon...'
Which meant the barrier would also work against him.
Sukuna's mood turned sour as he looked at the villagers and said.
"You guys go ahead without me... I'll just wait here for you to return..."
He handed them several gems he had taken from the dungeon and told them to acquire magic knowledge using the money while looking for the architecture.
After the village men left, Sukuna wore a coat and pulled up its hood before sitting down and leaning against a random tree.
With the help of memories he got from Sukuna, his control over his mana was incredible, meaning he was able to suppress it to a large degree like Frieren and Serie.
So he kept it suppressed to avoid gathering unwanted attention while he was near the human city.
As he was waiting, he saw several carriages going towards the city.
Just then he noticed something.
It was a decently large amount of mana.
Well it was much smaller than what he had but it was incomparable to any other mana source he had sensed before.....
Just as he was thinking, the answer revealed itself.
It was a man, floating in the sky.
With a single red horn present on his forehead.
'A demon?'
Sukuna narrowed his eyes.