Chapter Text

Chapter One: Beneath the Surface

The sound of waves crashing against the shore filled the air as the scouts trained on the beach, their boots sinking into the damp sand with each movement. The sun hung low in the sky, casting a golden hue over the water, which glistened like a vast mirror. It was an unfamiliar, almost surreal sight, far removed from the rocky cliffs and forests they were used to. Yet the beach had become their new training ground, a place to hone their skills after the brutal battles in Marley and the internal struggles back on Paradis. 

Eren stood silently at the water's edge, his green eyes fixed on the horizon. His posture was rigid, his expression unreadable, like a statue carved from stone. He had changed so much since returning from Marley . The softness that had once lingered in his gaze was now gone, replaced by something colder, more calculating. He was their leader now, an unofficial king who had seized control through force and necessity. And with him, Floch stood like a shadow, always near, his red hair catching the sunlight as he scanned the area for potential threats.

Levi stood a few paces behind Eren, arms crossed, his sharp gaze constantly shifting between the scouts and their surroundings. His ever-present vigilance had not waned despite the apparent calm of the beach. The tension in his jaw was palpable—, but nothing could dampen his fierce intensity.

The rest of the scouts were scattered around, practicing maneuvers with their ODM gear. Jean was discussing strategy with Connie and Sasha, their voices rising and falling as they argued over formations. Armin stood beside Mikasa, pointing out something in the distance, his soft tone contrasting with Mikasa's silence. Since her confrontation with Eren, Mikasa had withdrawn into herself even more, her usual loyalty tempered by the harsh truth Eren had thrown at her. Still, her eyes never left him, always watchful, always yearning . Bertholdt and Reiner, despite their history with the scouts, now stood as allies once again, though the air between them and the others was still thick with tension.

Onyakapon and Yelena stood further back, observing the group. They had been instrumental in guiding Paradis toward this new reality, though their loyalties often seemed as enigmatic as the secrets they carried. Today, however, they seemed more at ease— until something caught Yelena’s eye .

It was subtle at first, a shimmer in the water, barely noticeable against the backdrop of the sparkling sea. But then, out of the corner of Eren’s vision, he saw it— a pair of bright blue eyes staring at him from beneath the waves.

" Oi ," Levi said, his voice low but commanding, as he followed Eren’s gaze. " You see that? "

The scouts paused, their movements halting as they followed Levi's line of sight. At first, there was confusion. The water looked empty, save for the soft ripples where the waves met the shore. But then they saw it—a glimpse of white, coiling hair just beneath the surface, and those piercing eyes, locked onto Eren with a gaze so intense it sent a chill down his spine.

“What the hell is that?” Jean muttered, his hand instinctively reaching for the hilt of his blade.

Mikasa stepped forward, her expression darkening. “ Eren… ”

But Eren said nothing. 

His eyes were locked with the figure in the water, unmoving. There was something about the gaze—something primal, magnetic, that stirred something deep within him. It wasn’t fear, but it wasn’t comfort either. It was as though this being, whoever or whatever it was, had known him forever.

"Stand down," Onyakapon’s voice cut through the tension. He moved forward, raising his hands in a gesture of calm. "It’s not what you think."

“What do you mean?” Armin asked, stepping closer to Onyakapon, his curiosity piqued. “Do you know what that is?”

Yelena smiled faintly, her eyes shining with a knowing look. “Not ‘what ,’ Armin. Who .”

The scouts exchanged confused glances. Sasha squinted at the water, her hand shading her eyes. "Looks like a person… but how?"

Onyakapon nodded. “That is a siren .”

" A siren? " Connie repeated, frowning. "Like the creatures in the old stories?"

“Exactly like that,” Onyakapon confirmed. “They live in the sea, incredibly powerful beings, and that one…” He pointed toward the figure whose eyes were still fixed on Eren. “She’s chosen him.”

Mikasa stiffened, her eyes narrowing. “What do you mean she’s ‘ chosen him’? ”

Onyakapon turned to Eren, his voice calm but filled with gravity. “Sirens choose mates, Eren. They seek out the strongest among men— leaders, warriors . They bond with them, and in doing so, they make their mates more powerful, more capable. In return, the man offers protection and loyalty for life.”

Eren remained silent, but his eyes never wavered from the figure in the water. The intensity of the gaze between them was palpable, as though the entire beach had vanished, leaving only the two of them locked in an unspoken conversation.

Floch sneered, glancing between Eren and the siren. “So what? She wants Eren? That’s ridiculous..”

“We’ve encountered them before,” Yelena interjected, her tone serene yet firm. Onyakapon and I, in another land. The sirens are real, and their power is undeniable.”

Armin’s curiosity deepened. “What kind of power?”

Onyakapon crossed his arms, his gaze now serious. “Their voices can compel men to do their bidding. They can summon great force through sound alone, enough to disarm entire armies. But they are not invincible. When they are on land, they lose their abilities. That is why they seek out strong men—to protect them when they are vulnerable.”

Levi remained silent, his eyes narrowing as he studied the siren. “And that’s what she wants with Eren?”

“Yes,” Onyakapon replied simply. “And to give him something in return— unimaginable power . Their bond will make him stronger than ever before. Faster. Smarter. A perfect warrior .”

Hange, who had been quietly listening, finally spoke up, her eyes glinting with interest. “ Fascinating… A symbiotic relationship with a creature of the sea. If it’s true, it could change everything about how we understand power dynamics.”

Mikasa, however, was far from fascinated. She took a step closer to Eren, her fists clenched. “ This is insane! We don’t know what she’ll do to you.”

Eren finally broke his silence, his voice low and steady. “ I’m not afraid .”

The words hung in the air, cold and resolute, as if Eren had already made up his mind. His gaze remained fixed on the siren, the strange connection between them deepening with every passing second.

For what seemed like hours, the siren’s gaze remained on him, unwavering and filled with a desire that was palpable even from a distance. The sun dipped lower, casting long shadows across the beach, but she never moved, her eyes locked on Eren’s, silently calling to him.

Finally, as the sky darkened and the sea glowed with the last light of day, the siren’s eyes disappeared beneath the surface of the water, her figure vanishing as silently as it had appeared. The waves continued their rhythmic crash against the shore, leaving the scouts standing in stunned silence.

Eren turned away from the water, his expression unreadable. But something had changed . Something none of them fully understood yet.

The rest of the scouts stood in silence, the air thick with confusion and unease. The figure in the water had vanished as mysteriously as she had appeared, but her presence lingered like a shadow over the group.

Mikasa was the first to break the tense silence. She stepped forward, her brow furrowed, hands clenched at her sides. “Eren… you can’t be serious about this.”

Eren turned his head slightly, but his expression remained unreadable, that same cold, detached look that had become all too familiar since their return from Marley. He didn’t respond, which only seemed to stoke the fire in Mikasa’s voice.

“ You haven’t even seen her face properly! ” Mikasa exclaimed, throwing a hand toward the sea as if pointing out the absurdity of the situation. “You don’t know what she really looks like, who she is, or what she really wants! She’s just some… some fish woman! ”

Levi’s eyes flicked to Mikasa, his usual stoic demeanor betraying a hint of irritation at the rising tension. The others watched in silence, unsure of where the conversation was even going.

Jean scoffed under his breath. “Yeah, how’s that supposed to work anyway? You’re a human, Eren, and she—she lives in the sea. This whole thing is—”

“ Ridiculous ,” Mikasa interrupted, her voice sharp and desperate. “You’re not seriously thinking about… bonding or whatever it is she wants, are you? With someone you can’t even—”

“ That’s enough ,” Eren’s voice cut through the air like a knife, low and commanding. He finally turned to face Mikasa, his eyes hard, but still carrying that distant, unreadable edge. “You don’t understand what’s at stake.”

Mikasa flinched, her lips parting to speak, but no words came out. The rest of the scouts shifted uncomfortably, sensing the unspoken tension between the two. Eren’s words weren’t just about the siren—there was more underneath, the weight of their fractured relationship bearing down on the conversation.

Armin, always the mediator, stepped forward. “Eren, I think what Mikasa is trying to say is… we don’t know anything about this siren. Or what this bond means for you.”

Onyakapon, sensing the need to clarify, spoke up. “I understand your hesitation,” he said, his voice calm but firm. “But sirens aren’t what you think they are. They don’t stay in the sea forever. They can take human forms . They’re vulnerable in that form, but like I explained before, that’s why they seek out mates—powerful warriors to protect them when they can’t protect themselves.”

Yelena nodded in agreement, her sharp gaze scanning the group. “It’s a delicate process. The siren won’t approach Eren on land until she’s certain he won’t harm her. They’re cautious by nature, especially when it comes to choosing a mate.”

“ Cautious? ” Mikasa’s voice was laced with frustration. “She spent hours just staring at him! She hasn’t said a word, hasn’t even shown her face. How is he supposed to trust her? ”

“She’s testing him,” Onyakapon explained. “It’s part of their nature. Sirens are selective. And she needs to know Eren can be trusted.”

Mikasa shook her head, her jaw clenched in disbelief. “And you think staring at him for hours is enough to decide that?”

Floch, who had been quiet up until now, let out a dry laugh. “ So, what? We’re really supposed to believe this sea creature can just give him some kind of power boost? Sounds like a trap to me .”

“Of course you’d say that,” Jean muttered, rolling his eyes. “You’d probably say the same thing if it were anyone else offering Eren power.”

Floch shot Jean a glare, but Yelena intervened before the conversation could spiral. “It’s not about power in the way you’re thinking, Floch. Yes, the bond makes the man stronger, more capable. But it’s not a trick. It’s symbiosis—both parties benefit. It’s been happening for centuries, in lands beyond Paradis. Many of the world’s greatest warriors and kings throughout history all owe their success to the bonds they made with sirens.”

Connie let out a low whistle. “So, Eren’s supposed to protect her when she’s human, and in return, she makes him... what? A super soldier? ”

“Something like that,” Yelena replied. “But it’s deeper than just physical strength. The bond affects everything—mind, body, and soul. It changes you.”

Mikasa crossed her arms tightly, her eyes still locked on Eren. “And you’re just going to go along with this? With someone you don’t even know? Someone who just watches you from the water?”

Eren’s eyes flicked to Mikasa, his expression hardening further. “It’s not about what I want. It’s about what needs to be done.”

Mikasa’s lips trembled as she struggled to find the right words, her emotions boiling over. “Eren… this isn’t you. You don’t need—”

“ I don’t need you to tell me what I need ,” Eren interrupted coldly, his gaze piercing into her. “I’ve made my choice.”

The words hit like a slap, and Mikasa visibly recoiled, her face paling. For a moment, it seemed like she might say something else, but she stayed silent, the pain in her eyes unmistakable.

Armin, sensing the tension rise even further, quickly tried to diffuse the situation. “We just need more information. If what Onyakapon and Yelena are saying is true, then we should at least understand what’s happening before making any decisions.”

Levi, who had been quietly observing the entire exchange, finally spoke, his voice as calm and cutting as ever. “Fine. But we don’t make any decisions until we know exactly what we’re dealing with. If this siren’s serious, she’ll need to prove she’s not a threat. We’ve been through too much to gamble on something we don’t understand.”

Eren gave Levi a sharp nod, though his focus remained on the sea. 

Mikasa’s gaze lingered on Eren for a moment longer before she turned away, her heart heavy with unspoken words and a growing fear she couldn’t shake. This wasn’t just about the siren. It was about losing him —losing him to something she didn’t understand, something beyond her control.

And in her silence, the waves continued to crash against the shore, the promise of something ancient and powerful waiting just beneath the surface.