The demon lord is my girlfriend

The night had fallen, and the Underworld's crimson sky deepened into a velvety shade of blood red, streaked with veins of gold and black. A massive golden moon hung low, its surface marred by jagged cracks that glowed faintly, as if the moon itself were bleeding light. The air was thick with the scent of sulfur and ash, and the ground beneath Naomi's feet was a sea of red sand—fine and powdery, shifting with every step he took. The desert stretched endlessly in every direction, broken only by jagged obsidian rocks that jutted out like the bones of some long-dead beast.

Naomi trudged forward, his silver eyes scanning the horizon. His hoodie was damp with sweat, and his breath came in shallow gasps. The heat of the Underworld was oppressive, but it wasn't the kind of heat that warmed you—it was a dry, suffocating heat that clung to your skin and made your throat burn.

I'm in the Underworld, he thought, his voice echoing in his head. If I were a normal person, maybe I'd panic. But I'm an otaku. I've seen enough isekai anime to know how this works.

He paused, looking up at the golden moon. "Is there some demon out there waiting to attack me?" he muttered, half to himself. "Or are you going to give me a superpower or something?"

The moon offered no answer, its golden light unwavering. Naomi sighed and took a deep breath, the air thick with the taste of metal and decay. He clenched his fists and started running, his legs burning with every step.

"When is this going to end?" he shouted into the void, his voice swallowed by the vast emptiness.

---

Four Hours Later

The desert finally gave way to a sprawling city, its skyline dominated by jagged obsidian towers that pierced the crimson sky. The city was a chaotic blend of ancient and modern architecture: towering spires of black stone stood alongside crumbling ruins, their surfaces etched with glowing runes that pulsed faintly with purple light. The streets were paved with dark, polished stone, and the air was filled with the hum of activity—shouts, laughter, and the occasional roar of some unseen beast.

Naomi stopped at the edge of the city, his chest heaving as he caught his breath. "This has to be where Aiko is," he said, his voice tinged with hope.

But as he stared at the city, a sudden realization hit him like a punch to the gut.

"Wait a minute," he said, his face twisting into a stupid expression. "How am I supposed to save her? I didn't even think this through!"

He smacked his forehead in frustration. "How did I not think about this sooner?"

Before he could spiral further, a strange noise caught his attention. It was a low, rhythmic hum, growing louder as he approached the city. Naomi crept closer, his curiosity piqued.

"What's going on here?" he whispered.

---

The Demon Parade

As Naomi entered the city, he was met with a surreal sight: hundreds of demons marching in unison, their forms illuminated by flickering flames. The parade was a spectacle unlike anything Naomi had ever seen. The demons were a diverse array of shapes and sizes—some towering over ten feet tall with horns and wings, others small and nimble with glowing eyes and clawed hands. Their bodies burned with fire, but they showed no signs of pain. Instead, they sang in a haunting, guttural chorus that sent shivers down Naomi's spine.

The streets were lined with more demons, their eyes glowing with excitement as they watched the procession. Some cheered, their voices rough and gravelly, while others clapped their hands or stomped their feet in rhythm with the music. The air was thick with the scent of smoke and incense, and the ground trembled with the weight of the marching demons.

Naomi's eyes widened as he took in the scene.

"Is this… a parade?" he muttered, his voice barely audible over the noise.

---

Koka's Introduction

"That's the Demon Parade," a voice said beside him.

Naomi jumped, turning to see an old woman with white hair and piercing blue eyes. She leaned on a long, gnarled stick, her expression calm but knowing. Her face was lined with age, but her eyes were sharp and full of life. She wore a tattered cloak that seemed to shimmer faintly in the light of the parade, and her hands were adorned with rings that glowed with a soft blue light.

"Whoa! Where did you come from?" Naomi asked, his heart still racing.

The woman chuckled. "I've been here longer than you, kid. The parade happens once a year. It's a tradition."

Naomi frowned. "What's the point of it?"

The woman—Koka—looked at him with a sly smile. "You're not from this world, are you?"

Naomi hesitated, then blurted out, "I'm from this world! I'm the son of King Satan!"

Koka burst into laughter, her voice echoing through the empty streets. "Humans are always the same. You can't hide when you're lying."

Naomi's face turned red. "Okay, fine. I'm not from here. But who are you?"

Koka's smile faded slightly. "I'm Koka. Just an old, weak woman."

Naomi's eyes widened. "Wait… you're human?"

Koka nodded. "Yes. And before you ask, no, I don't know if there are others like me. The Underworld isn't just for demons, but they're the majority. Racism is alive and well here."

The Cloak of Shadows

Koka studied Naomi for a long moment before tapping her gnarled stick against the ground. A pulse of blue light rippled outward, making the air shimmer. Before Naomi could ask what she was doing, the light condensed into a swirling vortex at the tip of her staff. From within, a black cape materialized, billowing as if caught in an invisible wind. It was lined with dark silver embroidery, the patterns shifting like living shadows.

"Wear this," Koka said, handing it to him.

Naomi hesitated before draping it over his shoulders. The fabric was cool to the touch, unnaturally light yet sturdy. As soon as he fastened it, he felt an odd sensation—like the world around him had dimmed just slightly. He lifted his hand in front of his face. It was still visible, but if he didn't focus on it, it seemed to blur into the background.

"It'll keep you from standing out too much," Koka explained. "The demons won't bother you as long as you don't do anything stupid."

Naomi pulled the hood up and looked at her skeptically. "Define 'stupid.'"

Koka smirked. "Attacking someone, getting in the way of the parade, running your mouth… the usual."

Naomi sighed. "Great. That's basically asking me not to be me."

Koka chuckled and started walking. "Come on. You wanted to see the Underworld up close, didn't you?"

---

The Parade Up Close

Naomi followed Koka through the winding streets, slipping into the crowd of demons. Up close, the parade was even more breathtaking. The air vibrated with deep, resonant chants, and the scent of burning incense thickened around them. Demons danced in the streets—some twirling massive flaming chains, others carving symbols of light into the air with their claws.

Above them, winged demons soared through the crimson sky in synchronized formations. Their wings flared with flames as they twisted and spun, leaving trails of golden embers behind them. It was like a fireworks display—except the fireworks were alive, sentient, and far too powerful for comfort.

Naomi's breath caught in his throat as he watched. "This is insane."

Koka followed his gaze. "The sky dancers. The most talented of the demon clans send their strongest fliers to perform each year."

Naomi squinted at them. Some demons had enormous bat-like wings, their black membranes glowing faintly at the edges. Others had multiple sets of feathered wings, their movements elegant and fluid, as if they were painting the sky with fire. Then, among them, he saw something eerily familiar.

There were demons who looked like Aiko. Not just one or two—several of them. Their sharp golden eyes, their curved horns, even the way their tails flicked in the air. And among them, there were others who resembled Komori.

Naomi felt his chest tighten. Aiko… she really is from here.

His gaze shifted to the rest of the crowd. Some demons looked like monstrous beasts, their jaws filled with jagged teeth, their bodies covered in scales or fur. Others had a more humanoid shape, but their features were sharp and terrifying—resembling the depictions of Satan he had seen in human mythology—towering frames, curled horns, and piercing, glowing eyes.

Despite their differences, they all moved together in perfect rhythm. Even the monstrous ones, who looked like they could tear the city apart, swayed to the music in a strangely hypnotic harmony.

"They don't look as… evil as I thought they would," Naomi admitted.

Koka glanced at him. "That's because the stories humans tell are incomplete. Demons can be ruthless, but they're not mindless monsters. They have culture, tradition, and pride. They just follow different rules than humans."

Naomi stared at the scene before him, feeling something shift inside him. He had come here expecting a world of horrors, but instead, he was witnessing something breathtakingly complex.

For a moment, he almost forgot why he was here.

The Sky Ablaze

As Naomi stood among the crowd, his eyes were drawn upward once more. The sky was alive. The winged demons continued their dance, moving in intricate patterns against the vast crimson expanse. Their movements were not random; they wove through the air in mesmerizing synchronization, like celestial performers painting the heavens with fire.

Some demons spiraled together, twisting like twin comets before separating in a burst of golden embers. Others dived toward the ground, pulling up just before impact, sending waves of shimmering sparks cascading through the air. The sheer speed and precision of their movements left Naomi breathless.

Then, as if the universe itself had decided to join the spectacle, streaks of light began to fall from the heavens. A meteor shower, brilliant and ethereal, ignited the sky. But this was no ordinary phenomenon. Each falling star carried a faint, ghostly aura, leaving behind trails of blue and silver light that shimmered unnaturally.

The crowd gasped in unison, and then—cheers erupted. The demons on the ground raised their voices in deep, guttural chants, their eyes reflecting the celestial display. Some stretched their hands toward the sky, as if reaching for the souls that passed through the void above.

Koka exhaled softly beside Naomi. "The souls of the lost."

Naomi turned to her, his heart pounding. "What?"

"The meteor shower," she said, her voice low, almost reverent. "Those aren't just falling stars. They are the wandering souls of the forgotten—those who perished without a place to call home, without a legacy to leave behind."

Naomi's breath caught in his throat. The sky was not merely burning—it was mourning.

As the meteors streaked past the massive golden moon, their ghostly light flickered as if whispering secrets to the world below. Some demons knelt, bowing their heads in silent acknowledgment. Others continued to cheer, their voices filled with reverence and excitement. It was not sorrowful, nor was it entirely joyous. It was something in between—a tribute, a remembrance, a celebration of those who had come before.

The winged demons responded to the celestial event, altering their flight patterns. They moved in harmony with the falling souls, following their trajectories, twirling through the sky like guiding spirits. One demon, with six magnificent wings wreathed in flames, soared to the highest point of the sky, then folded its wings and plummeted like a comet. At the last moment, it flared them open, sending a shockwave of golden light rippling outward.

The crowd roared in approval.

Naomi could do nothing but stare.

For the first time since arriving in the Underworld, he wasn't thinking about survival. He wasn't thinking about Aiko, or danger, or the mission he had forced upon himself. He was simply watching.

And for a brief, fleeting moment, he understood.

The Underworld was terrifying. It was foreign. It was dangerous.

But it was also beautiful.

Koka tapped him lightly with her staff. "Come on, kid. Take it in while you can, but don't forget—you're still an outsider here."

Naomi pulled his gaze away from the sky with difficulty. "Yeah… let's go."

As he turned to follow Koka through the winding streets, one last meteor blazed across the sky, leaving a trail of silver fire in its wake. Naomi watched it vanish beyond the city's skyline, a quiet thought echoing in his mind.

Who do you belong to?

---

Koka's House

Koka led Naomi to a small, two-story house on the outskirts of the city. The interior was cozy but cluttered, with strange artifacts and trinkets scattered about. Naomi's eyes landed on a peculiar hat sitting on the table. It looked oddly familiar, but he couldn't place where he'd seen it before.

"You'll stay here," Koka said, sitting down in a worn-out chair. "The demons won't find you."

Naomi nodded, still staring at the hat. "Thanks. But… why are you helping me?"

Koka reached into her pocket and pulled out a white flower. She lit one end and began to smoke it, the scent of vanilla filling the room. "I heard someone from the Underworld has been visiting the human world recently. I assume that's why you're here."

Naomi's heart skipped a beat. "Yes. She's my friend. Her name is Aiko. Do you know her?"

Koka's expression darkened. She took a long drag from the flower, her blue eyes locking onto Naomi's. "Klaus o Aiko," she said slowly. "That's the name of the 14th Demon King."

Naomi's blood ran cold. "What?"

Koka leaned forward, her voice low and grave. "Your friend is one of the five Demon Lords. And she's the daughter of the Demon King."

Naomi's mind reeled. I have to fight the Demon King to save her? That's impossible.

Koka's gaze softened slightly. "You've got a lot to learn, kid. But for now, rest. You're going to need it."