He had been summoned to this world as the Demon Lord for over five hundred years. Although he had stopped counting after three hundred years, so he wasn't sure of the exact number.
At first, he was incredibly excited. After all, he was summoned to a fantasy world like those in manga and novels. However, he was summoned as the Demon Lord.
Being the Demon Lord might be a classic trope, second only to the hero, but it was still bewildering. But still, he was hopeful about being summoned to another world.
A year or two after his summoning, when he had gotten used to life in this new world, a hero, summoned by the humans, arrived at the Demon Lord's castle with nothing but the intention to defeat him.
The battle with the hero was fierce. The hero, wielding a holy sword, cut down thousands of monsters in a single swing and mowed down the demons. His advisors at the time said it was like watching the embodiment of injustice.
But he didn't give up. He deployed many skilled demons under his command and showcased unique magic, using knowledge from his previous world.
In the end, the Demon Lord's castle was heavily damaged, and after many sacrifices, he narrowly defeated the hero.
He was genuinely happy to have defeated the hero. Above all, he was glad to have protected the demons he had grown fond of. He hoped for a ceasefire and a happy ending with the humans. There might be some complaints from the demon side, but he, originally a human, didn't want to annihilate all humans. If possible, he wanted coexistence; if not, then non-interference. He hoped for coexistence.
But his wishes didn't come true.
Suddenly, the hero's sword—the holy sword—began to glow. It floated by itself and impaled the hero who was right next to it. Everyone present was too shocked to react. By the time they came to their senses, the hero was dead, and the holy sword had vanished without a trace.
He couldn't understand what had happened.
Why did the holy sword kill the hero? Where did it go? What was that holy sword, to begin with?
The battle with the hero concluded, shrouded in mystery. The atmosphere among the demons was heavy. Especially for him, who heard the hero's dying words and was profoundly affected.
"I... don't want... to die..."
Seeing the hero, who pleaded with despair in his eyes, he understood for the first time the essence of taking a life.
After the battle with the hero, he spent his days listlessly. His soul seemed to have left his body. His close aides were deeply concerned and cared for him. This gloomy atmosphere continued for several months.
Then, thanks to the efforts of his aides, he began to recover, albeit slowly. But then the hero appeared before him again, holding the same "holy sword" as before.
He was perplexed. Why was the sword there? Why did the hero have it?
All he could conclude was that he needed to destroy the holy sword. But no matter how much magic, blows, or slashes he applied, the holy sword wouldn't break. And just like before, the sword took the hero's life and vanished into the light.
He finally realized that defeating the hero time and again was meaningless. It was the holy sword that needed to be defeated.
Years later, despite his previous experiences, the hero appeared before him again, wielding the holy sword.
He proposed to the hero that if he handed over the holy sword, the demons would promise not to interfere with humans at all. But the proposal was rejected. In the end, history just repeated itself.
Years later, the hero appeared again and died right before his eyes. The same thing happened over and over again, wearing down his mind severely. Watching people die in front of him was torturous for someone who came from a peaceful world.
But what kept him from breaking were the demons who supported him.
Ilm, who supported his almost broken heart.
Gainos, who taught him swordsmanship.
Rem, who developed new magic with him.
All the servants in the castle.
All of them were irreplaceable, warm beings. But even they were taken away mercilessly by the holy sword.
One time, when the hero visited, the Demon Lord was prepared. He was now able to defeat the hero on his own. For some reason, his power or "level" had risen due to defeating the hero many times. He didn't have a skill to check stats, but he inferred from the hero's reactions.
He waited alone on his throne for the hero, keeping everyone else away to avoid the aftermath of the battle. But the hero didn't show up, even though he should've entered the castle by now. Feeling anxious, he searched for the hero's magical presence.
The hero's magical signature was indeed inside the castle, but the location was problematic. He rushed to the basement, breaking through floors.
By the time he reached the basement, it was too late. The floor was drenched in blood, and body parts were scattered everywhere. They belonged to the beings who had been like his family in this world.
He couldn't understand why. He had set up multiple barriers and even separated the dimensions. But all of it had been in vain.
The numerous answers to the questions that swirled in his chest were in the hands of the hero, standing calmly amidst a sea of blood.
-- The Holy Sword.
"Ahh, I see," he understood. In front of the Holy Sword, barriers were as flimsy as paper. Even if you separated dimensions, this sword would simply slice through those dimensions. It was that sort of thing.
Despair filled his heart.
The family that supported him, the ones most dear to him, had been taken away root and branch. An unbearable sense of loss gnawed at him, both physically and emotionally. There was a moment when he wished to die right then and there.
Something rolled to his feet.
He immediately understood what it was. But his heart refused to accept the reality.
Adding insult to injury, the hero said,
"Aww, too bad. I rather liked that woman. I was thinking of keeping her, but what's this about a Demon Lord? She was too persistent, so I roughed her up."
The hero, with his inconceivable words, laughed heartily. Those words snapped something taut within him.
"Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaah!!"
Despair was overtaken by rage.
Releasing all his power, he went berserk.
He killed the hero and, unsatisfied, invaded the human continent on his own, attacking cities and towns at random, laying them to waste.
To humans, his furious rampage must have seemed nothing short of a catastrophe.
After exhausting his rage, he stood amidst the rubble of collapsed buildings.
He'd lost what he wanted to protect. He'd lost the will to fight. He'd lost the meaning of life. He felt like an empty shell.
He was tired.
-- I'll die.
With that thought, he poured all his magic power to activate a spell. Centering on himself, he triggered a massive explosion, transforming the once-thriving city into a vast crater.
In the center of the explosion, he lay on his back, with a look of incomprehension on his face.
The spell activated. There was pain. But he didn't die-- he couldn't.
Even when taking a spell powerful enough to scatter his body into pieces at close range, or piercing his chest with a sword. There was pain, but death didn't come.
In the end, he even exposed himself to the hero's Holy Sword. But his body endured even that.
The sheer number of times he'd defeated the hero, his increased levels and stats had a side effect. Due to becoming too powerful, he gained a kind of pseudo-immortality.
When he realized this, he despaired again.
Unable to end his own life, he was doomed to endlessly fend off the hero in his empty castle.
It was as if he was cursed.
Someone, anyone... please, kill me.