Midnight.
Kazama Aoi was jolted awake by the sound of faint, rustling footsteps.
She sat up instantly, her hand instinctively flying to the hilt of the Nichirin Sword resting beside her.
"Who's there?" Muichiro asked, rubbing his sleepy eyes as he peered toward the doorway.
"Hmph, what do we have here? Just two stinking brats," a coarse, raspy sneer drifted from the shadows of the courtyard, accompanied by the thick, cloying scent of blood.
"Muichiro, look out!"
Yuichiro grabbed Muichiro and hauled him backward. Muichiro's hand froze mid-rub; as soon as his eyes adjusted to the terrifying silhouette of the demon lurking in the dark, his entire body locked up in fear.
The demon lunged, its jagged claws sweeping toward the pair. Yuichiro shielded Muichiro behind his back, his small frame trembling with resolve.
"Stay back!"
A split second before the demon reached the boys, Aoi's Nichirin Sword whistled through the air.
"Wood Breathing, First Form: Sprouting Slash!"
The demon didn't even have time to process the movement before its head was severed by the fierce arc of the blade. Dark blood splattered across the ground, only to dissolve into fine, gray ash an instant later.
The demon's headless torso froze mid-lunge before crashing to the floor, disintegrating before their eyes. Within seconds, nothing remained but a faint, lingering stench that the night breeze quickly swept away.
"What... what was that?"
Yuichiro's voice was brittle and shaky. He remained in his protective stance over Muichiro, his fingertips trembling. Though the terror hadn't quite left his eyes, he forced himself to look at Aoi with a facade of composure.
Aoi sheathed her sword and knelt down to meet their gaze, her voice softening significantly. "That was a demon—a monster that feeds on humans."
Muichiro peeked out from behind Yuichiro, his tiny hand clutching his brother's hem. He whispered the word back like a curse: "A demon...?"
Aoi nodded gently. She reached out, touching the back of Muichiro's cold hand before ruffling his soft hair. "Yes. They only come out at night to hurt people. They fear the sunlight and the Nichirin Sword."
"Nichirin Sword?"
Aoi gestured to the blade at her hip. "This is it. A sword forged specifically to slay demons. It's the only thing that can truly destroy those monsters."
Yuichiro stared at the sword, a look of deep contemplation crossing his young face.
Just then, the elder Tokitos rushed out from the inner room. After realizing what had happened, they pulled both boys into a tight embrace, their hands trembling as they stroked their sons' backs. They turned to Aoi and bowed deeply, their voices thick with gratitude and lingering horror. "Miss Kazama, thank you... If you hadn't been here, these two children might have..."
Aoi stepped forward to gently help them up, shaking her head. "Please, there's no need for that. I am a member of the Demon Slayer Corps. It is my duty to slay demons and protect people. However, since a demon appeared so close to your home, you must be extra vigilant at night from now on."
Suddenly, a sharp system alarm blared in Aoi's mind.
[WARNING! WARNING! Due to the Host altering a critical plot node, you are being forcefully returned to your original timeline!]
An invisible, crushing force surged around her, dragging her consciousness toward a void.
Yuichiro noticed the change in Aoi's expression. "Aoi? What's wrong?"
[Space-time transport initiated. Countdown: Three... Two...]
Aoi's figure began to grow translucent. She looked at the panicked Yuichiro and offered a small, bittersweet wave. "Goodbye."
[One. Transport complete.]
When Aoi opened her eyes again, she was back in the small courtyard where she had been before her trip through time.
She stood there for a moment, dazed by the sudden shift in reality. She wasn't even sure how she made it back into her room, but the moment she pushed the door open, the sight inside froze her in her tracks.
"Yuichiro?"
The name slipped out instinctively. Her gaze was locked onto the small figure sitting by the low cot in the room.
The boy turned around. When he saw Aoi, he looked just as stunned as she was. "You..."
"How did you get here?!" Aoi rushed over to him, her eyes wide with disbelief. This wasn't supposed to happen!
"I don't know," Yuichiro admitted, a trace of panic in his eyes. "After you disappeared that day, I felt this weird suction pulling at me. Everything went blurry, and when I opened my eyes, I was in this room." He paused, his voice dropping to a whisper. "I don't know what happened to Muichiro... or Mom and Dad."
As Aoi struggled to make sense of the situation, the System's voice chimed in.
[Ding! Detected 'Force of Aspiration' from beyond this world. The 'Unresolved Regret' Instance Mission is now active. Target 'Yuichiro Tokito' has been successfully saved. Reward: 10,000 System Points.]
"Aspiration? Unresolved Regrets? How are you defining 'Unresolved Regrets'?" Aoi demanded internally.
[Definition: A character who suffers an irreversible tragic ending in the original timeline, where said ending triggers a high-concentration emotional resonance from outside the world, forming a stable Field of Aspiration.]
The mechanical voice was cold and indifferent. A holographic screen flickered to life in Aoi's mind, listing Yuichiro's original fate in blue text that made her heart clinch.
[Yuichiro Tokito: In the original timeline, he was killed during a demon attack at age 11. His death became Muichiro Tokito's lifelong trauma and was one of the core 'Unresolved Regrets' of this world. Aspiration Field Concentration: 99%. Requirement met.]
The words were like thorns. That sharp-tongued, soft-hearted boy—the one who always put his brother first—was supposed to have died at eleven under a demon's claws. He was supposed to have become the ghost that haunted Muichiro for the rest of his life.
Aoi looked at him, her gaze hardening with a new sense of purpose. She took Yuichiro's hand.
"Yuichiro, listen to me." Her voice was gentle but incredibly solemn, forcing him to meet her eyes. "You are in a different timeline now. There is a Muichiro here too, but in this world... you died during that demon attack when you were eleven. You left him all alone."
Yuichiro's face went pale. "What? That's impossible!"
He sat in stunned silence for a long time before choking out a question. "I... I died? Then... Muichiro..." He swallowed hard, his voice breaking. "He was all by himself? Was he scared?"
"The Muichiro of this timeline..." Aoi's voice grew even softer, but she didn't shield him from the truth. "He became the Mist Hashira of the Demon Slayer Corps. He became incredibly powerful and has slain countless demons."
Yuichiro couldn't bear to imagine it—Muichiro facing those hideous monsters alone, surviving night after night with no family left to turn to.
He was the older brother. He was supposed to be the shield.
But in this world, instead of protecting his brother, he had become his brother's greatest regret—a scar etched into Muichiro's very soul.
"I... I failed him..." Yuichiro's voice hitched, a sob catching in his throat. "I'm the big brother. I was supposed to protect him, but I..."
He couldn't finish. His small body began to shake uncontrollably.
"It's okay, Yuichiro. You did the best you could." Aoi pulled him into a hug, her palm resting on his trembling back. "You were just a child. None of it was your fault. It was the cruelty of the demons and the unfairness of fate."
It took a long time for his sobs to subside. Finally, he lifted his head from her shoulder, his eyes rimmed with red.
"I want to see Muichiro."