Small peek in history:-
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50 years ago a person was summoned from overworld to save this world from the terror of Demon Lord Yakub. That person soon became the infamous Great Hero Thunder Tusk. Thunder Tusk united all adventurers against the demons and created a whole organisation called National Union of Adventurers having adventurers from rank F to rank S tier adventurers. Everyone undergo through new revaluations except Great Hero Thunder Tusk who was beyond such power scaling. Just within decade of his summon, Thunder Tusk killed Demon Lord Yasub with his whole army. Many Demon Lords who were alongside Yakub too died and a huge army of demons was reduced to none. Whole world praised Thunder Tusk as humanity's Greatest Hero ever summoned.
Just when peace was spreading throughout the world, another Demon Lord announced a war. This time all 8 Demon Lords who were still alive will collaborate and will wipe all of adventurer who will cross their way. In this very war, Thunder Tusk was betrayed by his ally named Gleno , the person he trusted most. After death of Thunder Tusk the morals of all other adventurers crushed. Each Demon Lord was atleast SS tier and fought like they were fighting against toddlers. This war became biggest disaster in human history with death of many adventurers and the demon army entered many kingdoms and spread violence, brutality and worst, a terrifying mindset of humanity's defeat, of thier light, their morals.
Gleno had acquired a lot of power by killing Thunder Tusk and ascended to Great Demon Lord. Embodiment of whole evil, of whole darkness. His rule was Merciless. He won't care if his victim is old man, kids or even a pregnant woman, all his punishments would be cruel and he would enjoy seeing others in agony to slightest bit. The human population itself was reduced by 70% within a decade was the proof of his cruelty. He had started a new era for demons, of evilly.
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Present timeline, Year:- 1200 AD
There were few towns ruled by A grade demons. They would tax people heavily and would also demand a fresh alive human as food for them every year. Also it was a rule that a demon may anytime enter the private property of humans and can do whatever damage the demon wants. Also demons were allowed to do whatever to humans who would dare to make angry stare. Many humans were even kept as servants or pets.
Among these towns was town Cen. It was not a wealthy town. It was quite far from the capital. It was ruled by A grade Demon Lian . Obviously a cruel tyrant with no mercy towards anyone. Lian would even eat his own demon sub ordinates (with lower ranks of course) if he felt like they were useless to him.
In this town lived an innocent kid of age 12 years named Derono. He was quite optimistic and loving kid. He was full of energy and sometimes chaotic but had no intention to harm anyone. His life was not better but he won't regret about the things he don't have, instead he was among those who feel grateful for what they have. He have a family to love him unconditionally and that's more than enough for him.
He felt his life to be best until the very dark night that stole all his happiness. That very night it was supposed to be Derono's 13th Birthday so he was roaming in forest collecting some firewoods and when he returned in town, it was burning. Demons couldn't control their urge and they just attacked the town to devour on humans. Derono was seeing this whole cruelty with his widen eyes with terror.
[Derono]: Aaaaaaaa!!!! Noooooo!!! Mother?!! Father?!
Derono just screamed in terror and ran towards his home. In the way he saw few heads of kids and people lying on the path. Derono was terrified and was scared to his life. Just then he heard scream of his friend Gala. She was lying nearby soaked with blood. Her limbs missing. Derono's eyes were burning with this image. He rushed towards her and embraced her.
[Derono]: I am here! Don't worry I will save you! Trust me! Please don't leave me alone!! What happened here?! Why is this happening to us?!
[Gala]: Nooo!! This pains a lot! Please kill me!! Free me.
Gala was crying with pain. Derono was shocked. Seeing her cry and beg for death. He was feeling pain in his heart himself. She didn't die of blood flow because the Demon that attacked her used a magic to keep her alive so that she can suffer for long.
Derono who couldn't see this any longer lifted his axe and stroke it on her head ending her eternal suffering for once. He was blank of any emotions. He was feeling void when suddenly a Demon started laughing loudly behind him. It was Lian who just happened to devour Derono's parents.
[Lian]: Well that was quite the show kid. I really loved it though I wanted to see her in agony for some longer time. Anyways I have brought something for you.
Saying that Lian threw heads of Derono's parents near his feet. Derono who had went emotionless having blank face suddenly felt something exploding inside him. A dark powerful aura starte emitting out of his body. His aura was easy to sense. Easy to sense? Anyone inside 100 metres can feel some stress on their body due to this Aura.
[Lian, in his mind] : Looks like he awakened himself into an adventurer, these pieces of shit usually awake their powers after 12 years age. Still I am A grade Demon so it won't cause me mu...
Before Lian could complete his thoughts, his head was at Derono's hand. Lian's body burning to ashes due to the burning Aura of Derono. Derono laughs like psychopath for few minutes and then announces loudly right there.
[Derono]: I am making this vow now!! I will end this Demon Era!!! This is my burning resolve !! I won't lose!! You hear me Great Demon Lord!!!!! I...I will create my own Army for you!! Just you wait for me!!
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THE END