​A hundred years ago, the peaceful Earth suddenly turned into a living hell.

​Creatures that later became known as demons emerged from various corners of the world. They slaughtered humans without mercy, destroyed civilizations, and brought major cities to ruin.

​The world's militaries tried to fight back. Tanks, missiles, fighter jets—even the most advanced weaponry humanity prided itself on—were deployed into the battlefield.

​Yet, it was all in vain.

​In the face of the demons' absolute power, human technology was nothing more than a pile of scrap metal. For years, humanity lived in utter despair.

​Until one day, a glimmer of hope finally appeared.

​A man named Kazuki Kaito successfully defeated a demon with the help of a mysterious entity that called itself a Spirit. That Spirit was named Yushin.

​This discovery rewrote human history.

​Humans finally learned that they could form contracts with Spirits to obtain powers capable of fighting back against the demons. From that moment on, Spirit Contractors began to emerge. Though they were few in number, their existence became humanity's beacon of hope. They were deeply respected, admired, and revered as the protectors of the world.

​And since that fateful day... Earth was never the same again.

​"Hmm..."

​Haruto closed the history book he was reading. He sat quietly in the corner of the school library. The evening sunlight filtered through the large window, illuminating his dark hair. His sharp eyes stared outside for a brief moment before he murmured softly, "The world really did change after that."

​Not far from him, several female students were secretly watching him.

​"Hey, look at that... Haruto-kun is reading."

"He looks so incredibly handsome when he's being serious like that."

​Faint whispers began to echo among them. Hearing this, Haruto could only let out a subtle sigh. Situations like this had already become a daily routine for him. As one of the most popular students in school, he often became the center of attention without ever wanting to be.

​Haruto turned toward the girls and gave them a polite smile. "Everyone, please don't be too loud. This is a library."

​"Eh?!"

​The girls gasped, startled.

​"W-We're sorry, Haruto-kun!"

"Yeah, we'll keep it down."

​Haruto gave a small nod. "It's fine."

​One of the girls lowered her head, her face flushing bright red. "By the way... Haruto-kun looks really handsome today."

"Yeah! Just like always!"

"Is that so?" Haruto smiled awkwardly. "Thank you."

​For a second, the air went completely silent. Then—

​"Kyaaa!"

​The girls covered their blushing faces in embarrassment. Haruto could only sigh in resignation.

​A few hours later, the school bell finally rang, signaling the end of the day. Students poured into the corridors, eager to leave. Haruto packed his books into his bag, getting ready to head home.

​Suddenly, someone clapped his shoulder from behind.

​"Hey, Haruto!"

​Haruto didn't even need to turn around to know who it was. The person speaking was also one of the school's popular students.

​"What is it, Ren?"

​Takeshi Ren grinned broadly. "How about a footrace all the way home?"

"No thanks."

​Haruto's response came without a single second of hesitation. Ren's smile froze instantly.

​"Eh? Why not?"

"No particular reason." Haruto lifted his bag. "I just don't want to."

"Oh, come on!" Ren immediately threw an arm around Haruto's shoulder. "It's been forever since we last raced!"

"We just raced three days ago."

"That is forever!"

​Haruto looked up at the classroom ceiling as if praying for strength. "Hah..." Ultimately, he gave in. "Fine."

​"Yes!" Ren pumped his fist in excitement.

​But before he could say anything else, another voice drifted from behind them.

​"Can you guys keep it down a bit?"

​The two turned around. A black-haired youth was leaning back in his chair, rubbing his eyes. Nemui Reo—another popular student, just like Haruto and Ren. He was their classmate, notoriously known for always being drowsy.

​"I'm trying to sleep here," Reo complained.

Ren laughed awkwardly. "Sorry about that."

​Haruto glanced at Reo. "Didn't you already sleep through the entire lecture earlier?"

"I only slept for a few hours." Reo let out a wide yawn. "That's nowhere near enough."

"Of course it isn't," Ren chuckled. "Well, how about we just walk home together instead? We'll postpone the race for now."

​Haruto nodded. "Whatever works."

​The three of them left the school together. All the way home, Ren talked nonstop about various random things. On the other hand, Reo kept complaining about how tired he was, while Haruto simply walked alongside them, quietly listening.

​Even though the world was still plagued by the threat of demons, their daily lives seemed as peaceful as any ordinary teenagers'. At least, for the time being.

​Nightfall.

​Haruto had just arrived home when he suddenly realized something.

​"...The book."

​He opened his bag and double-checked the contents. It wasn't there. The history book he had been reading earlier was left behind in the classroom.

​Haruto sighed deeply. "Seriously..."

​Whether he liked it or not, he had to go back to school. Fortunately, his house wasn't too far away.

​A few minutes later, he arrived at the completely deserted school gates. The night sky was covered in dark, heavy clouds, leaving the corridor lights as the only source of illumination. With quiet steps, Haruto slipped inside.

​It didn't take long for him to retrieve the forgotten book from his classroom.

​"Alright." He gripped the book tightly. "Now, time to head back."

​However, just as he was about to step out of the classroom—

​"Hahahaha..."

​An unfamiliar voice suddenly echoed through the silence. Haruto stopped dead in his tracks. His eyes narrowed.

​The voice was clear, yet he couldn't pinpoint exactly where it was coming from.

​"Why is there a little ant here?" the voice mocked, its tone dripping with absolute derision.

​Haruto instantly put up his guard. "Who's there?" He scanned his surroundings sharply. "Come out. Stop hiding."

​"Hoh?" The voice sounded genuinely amused. "This little ant turns out to be quite brave."

​A tense silence filled the room. Then...

​"Very well."

​The impenetrable obsidian shadows slowly crept across the silent classroom, swallowing the remaining twilight. The air grew suffocatingly heavy, pressing down on Haruto’s chest like a physical weight.

​From the depths of that unnatural darkness, a humanoid figure began to coalesce. Its form was draped in a swirling vortex of malevolent black aura. A pair of crimson eyes snapped open, gleaming like burning coals in the dark, fixing their intense gaze directly upon Haruto. The creature's face exuded an aura of pure, unadulterated dread.

​Haruto froze. Every muscle in his body refused to move, paralyzed by the sheer pressure radiating from the entity before him. Time seemed to stand still.

​The creature’s lips curled into a faint, enigmatic smirk.

​"To think a mere mortal would possess such audacity," the figure spoke. Its voice was deep, resonant, and carried an undeniable, ancient authority that shook the very air. "And shouldn't humans have long abandoned this place when the sun goes down?"

​Haruto swallowed hard, forcing his trembling throat to work as he desperately tried to find his courage. "Wh-who are you?"

​The entity tilted its head slightly, observing him. "I am under no obligation to reveal my identity to you, human."

​It paused for a brief moment, the glowing red eyes narrowing in curiosity. "However... since you are the first mortal who has managed to look directly into my eyes without losing consciousness, I shall grant you a name."

​The black aura surrounding the creature flared and rippled violently.

​"I am the current sovereign of the Spirit Realm."

"The Spirit King, Rei."

​Haruto’s eyes widened in sheer disbelief. "The Spirit King...?"

​Rei stared at him for a few seconds, as if measuring the worth of his soul, before asking, "Human, what is your name?"

​"Tatsuki Haruto," he replied honestly, his voice barely louder than a whisper.

​Rei went silent. His piercing gaze seemed to weigh options that Haruto couldn't possibly comprehend. After a few agonizing seconds of silence, the sovereign finally opened his mouth.

​"Haruto."

"Form a contract with me."

​Haruto’s mind went completely blank. His brain scrambled to process the words that had just echoed through the room.

​"...Eh?" He stared at Rei, utterly bewildered. "Why me?"

​Rei remained perfectly nonchalant, as if discussing the weather. "Because you are the only human brave enough to stand before me." Then, his tone dropped into a flat, absolute finality. "Oh, and by the way, refusal is not an option."

​Haruto could only stare in silence. Even though the words were framed as a proposal, the underlying tone made it crystal clear: this was an absolute command from a supreme being.

​"Right... okay," Haruto managed to mutter.

​Upon hearing the answer, Rei materialized a unique parchment from the shadows. With a sharp flick of his wrist, he nicked the tip of his finger, allowing a drop of dark blood to well up, which he then pressed firmly onto the paper.

​Rei then turned his gaze toward Haruto.

​Understanding the unspoken instruction, Haruto didn't ask any further questions. He bit his own finger and pressed his blood right next to Rei's. The moment Haruto’s blood touched the parchment, the paper erupted into a dim, ethereal glow.

​Within a second, the parchment dissolved into thin air. At the exact same time, a searing sensation flared up on Haruto’s and Rei's hands as an intricate command seal etched itself onto their skin.

​Haruto stared at the glowing mark on his hand, completely mesmerized. It was the very first time he had ever witnessed a formal Spirit Contract being bound right before his eyes.

​"The contract is sealed," Rei said calmly.

​Haruto blinked a few times, trying to shake off the daze. "Is that really it?"

​Rei nodded. "Yes."

​Before Haruto could utter another word, Rei’s physical form suddenly dissolved into a dense cloud of black mist. The dark aura surged forward, coiling around Haruto before plunging directly into his chest.

​"What—?!"

​Haruto gasped in panic. But before he could even attempt to fight it off, his vision blurred instantly, and darkness claimed him.

​In a mere fraction of a second—

He opened his eyes to see a familiar ceiling. He was back in his own bedroom.

​Haruto bolted upright, looking around the room in absolute confusion. "My room...?"

​He immediately lifted his hand to check his skin. The intricate contract seal was still etched vividly on his hand. He sat there in dead silence for a long time, trying to ground himself before finally whispering into the quiet room.

​"Spirit King... are you still there?"

​Suddenly, a voice resonated clearly inside the confines of his own mind.

​"Yes, I am still here," Rei’s voice echoed smoothly. "And just call me Rei."

​Haruto let out a long, heavy sigh of relief. At the very least, he knew he wasn't losing his mind or hallucinating.

​But the peace didn't last long. A thick stream of black aura began to seep out from his chest. The darkness gathered in the center of the room, swirling rapidly before gradually taking the shape of a person.

​Haruto’s heart skipped a beat.

​The figure emerging from the shadows was undeniably Rei—but the physical form he took this time was completely different from the terrifying monster in the classroom.