In the following time, they decided to continue exploring floor by floor, instead of settling down to train in just one place.
Their adventures led to encounters with increasingly diverse and deadly types of monsters.
Even so, El still doesn't intervene. It was Hajime and Yue who faced the monsters, under El's conditions of course: conditions that became more and more unreasonable by the day.
For Hajime, El forbade him from using firearms for an entire hour in battle, forced him to fight and wouldn't even allow him to consume Ambrosia while injured.
In some cases, Hajime had to face 100 monsters at once without Yue's help with no hands and closed eyes, in order to train his fighting instincts and physical endurance.
Yue was not spared from the same treatment. El limited her use of magic to only one element per battle, forbade her from flying when facing land monsters, and had her create combined spells from two to four different magics.
In fact, it was not uncommon for Yue to be baited by monsters for a full three minutes, giving Hajime time to set up an ambush, arguing that this was an exercise in trust and reflexes.
However, El had his reasons.
He knew that every fight should always push them to their limits.
Hajime continued to grow stronger by eating the flesh of monsters, strengthening his body from within, while Yue already had very powerful magic from the start, only needing to be forged in real pressure and danger.
The monsters they encountered along the way included Sham Alraune.
A humanoid creature, with the ability to physically control other creatures using its unique parasitic pollen spores that it spreads in the air.
Giant Wasp: A giant wasp monster the size of a baby that can release a barrage of stings that explode on contact.
Praying Mantis: A giant praying mantis that can shoot blades of wind.
Giant Spider: Giant spiders with incredibly strong webs that are used to create traps and capture their prey.
Giant Ants: Giant ants that can attack their enemies from underground with a surprise attack.
Black Butterfly: A black butterfly that has the effect of paralyzing the person touched by the scales it releases.
But that's actually just a trick, the butterfly's special magic is actually a hypnotic magic that activates after the target sees the pattern on its wings.
From these battles with increasingly absurd conditions, at least Hajime and Yue had touched the basics of the Total Breathing Concentration that El taught them.
Although not perfect, this was more than enough for them. It only took a few more touches of life and death combat, then Total Breathing Concentration had been obtained by Hajime and Yue.
And in the future, it was likely that Hajime would not only get the Limit Break Skill.
More importantly than all that, as El went down the stairs to the floor deeper and deeper, something calling out to his was sending out stronger and stronger signals, making El feel somewhat uneasy.
Even so, with extraordinary self-control, El was able to ignore the uneasy feeling.
Finally, they arrived at a floor with a landscape surrounded by white rocks resembling solid old marble, as if it had stood for thousands of years.
El looked around and strongly suspected that this was the last floor, where the real boss awaited.
Hajime and Yue walked beside him, their eyes vigilantly scanning every corner. The atmosphere was different, quiet, yet full of invisible pressure.
Some of the marble formed steps that became the main access from the previous descending staircase. However, the décor of this room feels odd.
The rest of the stairs do not lead in a conventional manner, but instead cut off towards mysterious dark spaces.
Most strikingly, a clear stream of water emerges from a spring hidden in the wall, flowing calmly like a small river, down the marble floor that is finely cracked by time.
Beauty and strangeness blended together, like a sign that the final test would not only test strength, but also the soul.
Soon, the three of them arrived in front of a giant door, decorated with carved ornaments in the shape of a Hydra, a warning of what awaited behind it.
Hajime took out something from inside the Storage Ring, then flashed a sardonic smile. "Time to show what Schlagen is..."
It was a long, strange level-like object covered in Monster fur. Once opened, its true form was revealed.
That was the Schlagen, an anti-mater rifle with magnetic acceleration technology, a cross between a Railgun and a Gauss Rifle.
Its barrel reaches three meters, and its firepower is ten times that of a Donner revolver. However, it could only fire one bullet before needing to be reloaded.
Thanks to the body that had been strengthened by the consumption of monster flesh and the brutal training El had given him, Hajime now possessed incredible strength and stability.
Hajime was even able to fire the Schlagen with just one hand, from the hip position, without losing accuracy, although the stopping power was enough to topple a tank.
Yue turned her head, silently looking at the giant weapon created by Hajime. Her gaze was calm, but the red glint in her eyes revealed an interest that could not be hidden.
Meanwhile, El just sighed and shook his head lightly. "My Disciple... true strength comes from hard work that almost killed you. You rely too much on firearms."
"Shut up, you crazy teacher," Hajime said sharply, his face instantly folded in annoyance as he recalled the inhumane training he had undergone.
Yue also looked at El coldly, her eyes sharp, ambiguous between anger and annoyance. He too was not spared from the brutal training that El mercilessly imposed.
El raised his left hand half-heartedly, then flicked the air in front of his face. Two small, barely visible waves shot out and hit Hajime and Yue's foreheads with perfect precision.
"Agh!"
"Ouch..."
"Correct your speech," El said with a faint smile that wasn't entirely friendly. "Why don't you ever learn? Now Yue, huh?"
Hajime and Yue both winced as they bent down, holding their foreheads. The pain was small but piercing, enough to remind who was in charge.
While Hajime and Yue were still wincing while holding their foreheads, El turned his attention to the giant door before them.
Both of El's eyeballs changed; the ripple-patterned Rinnegan with six tomoe flashed briefly, emitting the heavy and silent aura of Samsara for a moment before returning to normal eyeballs.
In his mind, El's voice echoed quietly, "Finally... the place that called me. But is it really Hydra's boss? I don't think so. The energy is... different from this world's Mana."
Hajime and Yue, who had recovered, stood back up and looked at El with sharp eyes, either irritated or wary.
But El ignored him. His focus was on something behind the door, something more important than his students' egos.
Without another word, El stepped forward. Each step was a soft echo on the white marble floor. He reached out his hand, touching the surface of the door.
El pushed it slowly, with complete control, making sure his strength didn't damage the structure that had stood for who knows how long.
The door slowly opened, revealing a grand hall that stretched out before them.
Tall pillars of purple crystal stone stood firmly, emitting a faint light that bounced throughout the room, creating a mysterious yet majestic feel.
El, Hajime, and Yue stepped in from a door located on a high podium, their footsteps echoing softly on the smooth floor.
"This is... amazing," Hajime murmured, his eyes sweeping the surroundings in amazement.
Yue remained silent as usual, but from the gleam in her eyes, it was clear she was absorbing every detail of this place with great interest.
Meanwhile, El walked in silence, his eyes sharply scanning the surroundings. A faint aura of tension was visible from his demeanor, something was calling him.
The deeper El stepped, the stronger the spiritual pulse that echoed within him, like a whispering voice from underground.
The three of them stepped to the left of the podium, silently tracing a side path that led to the stone stairs leading down and into the deepest part of this place.
As they descended the stairs, their gaze fell on a luxurious stone throne at the end of an empty hall... or so it seemed?
At least, that was what El thought.
On the other hand, the spiritual pulse that had been reverberating inside him was getting crazier, as if it was coming from that place.
Something there kept calling his, urging his to step closer.