In the murky depths beneath the city, the weight of civilization bore down upon stone, laying the foundation of a realm shrouded in shadow, silence, and secrecy. The sewers were expansive and empty, perfect for the two wanderers that treaded through the tunnels that ominous night. A short woman cloaked in black as long and dark as her hair glided along with an air born of resignation. She was Tsubaki Aoyagi, a girl of nothing noteworthy, with a name of nothing noteworthy. She wasn't a Tohsaka or a Shimizu. Yet summoned by the Grail still she was, to fight in its War.
Her black combat boots clacked on the slimy ground, drowned out by her siren song. Like a hurricane she came, powerful, from the water, voice soft at first, but rising just as swiftly as a deadly tide. She would flood them out before they even knew what hit them! A melancholy melody floated up from the darkness of her throat, lingering in the air like a misty, lamenting phantom. It was her soul's unrest manifested, using the most powerful tool in her arsenal: her voice. She was a mage who cast spells not just with gesture or incantation, but song.
Trace… on! Tonight, she sought the Grail, and this city contained the next clue, one step closer to it. Gliding beside Tsubaki was her Servant, Rider. She was a purple-tailed, purple-haired mermaid who traveled by an ever-present wave of water, even on dry land. Like Tsubaki, she was a creature of sorrow, salty tears and sea. She was a water spirit, a water nymph. Her short, purple locks framed teary, teal eyes, an ocean mist creating a veil to conceal some of her eternal grief and loss from any who dared look upon her misfortune.
There wasn't a doubt in Rider or her Master's minds that their shared depression was what the Grail used to bind them together. The red thread was all over Tsubaki's inner forearm, her Command Seals! The duo navigated the sewers, path ahead lit only by the dark blue light Tsubaki's siren song spell spread. Water trickled from unseen crevices, forming rivulets that meandered down arched walls, across jagged floors.
They heard a crackle, a hiss, and then—"Ahahahaha!" An amused and triumphant bellow of laughter echoed behind Rider and Tsubaki. They whipped around, Servant quick to glide protectively in front of Master, the mermaid's wave growing taller and stronger as she prepared for battle. What stepped from the shadows was a smug, casual girl about as short as Tsubaki, but that was where the similarities ended. The other girl had wild, orange hair, done up in two, big, poofy pigtails, and she wore white while Tsubaki was clad in black and blue.
"Who are you?" Tsubaki hissed, the echoes of her song still reverberating through the sewers as her magic sustained itself.
"The Hero of this story! The Protagonist of this Grail War! Fate/blue!" The other girl jerked her thumb at herself proudly, orange eyes drifting shut.
Oh. Ok. So she's insane then. Tsubaki entered a battle stance as well. I'm noticing a trend here in the Grail War Masters… She was no Heroic Spirit, but she was still a mage! And this girl… As… weird as she is, she still snuck up on me, didn't she…? Where is her Servant…?
"I'm Rika! Rika Seto!" The orange-haired girl instead continued to introduce herself, hands on hips, chest puffed out, eyes still shut in self-satisfaction. "And the Grail ordained me the victor of this most holy war. It is I who will succeed and finalize my most perfect wish!"
"Which is…?" When the girl didn't continue, Tsubaki decided to bite and take the bait. Orange eyes finally opened, and the smile Rika gave Tsubaki was no longer so innocent, sweet, and friendly.
To be THE HERO! Ah, what she wouldn't have given to have summoned Saber! Seto was no noteworthy name either, but Rika was a little more savvy to the Grail War than Tsubaki (not that that was saying much, the latter learning about it the day her Servant nearly gave her a heart attack, swimming up at her from the harbor at the edge of the city she called home). Rika was far more intentional in her attempts to fish for a Servant, alas, she didn't snag the one she wanted. Oh well, she liked the one she had perfectly fine!
"Oh, Caaaaster…?!" Cupping her hands around her mouth, Rika sing-songed into the darkness of the sewers. What came clawing towards her was so inhuman it made Tsubaki's mermaid look normal.
Demon! The Master thought, recoiling in horror as a large, dark monster dragged its way closer and closer.
Prometheus! The Servant recognized her Caster equivalent immediately, and the moment his burning eyes met hers, she knew he recognized her too.
Ophelia! The drowned, the sorrowful. Like snakes, the waters rose up and dragged her down centuries ago… Tears snaked down her face as she lost her love—then her life—to madness. Whether Rider wanted to admit it or not, she was still searching for that lost love all these centuries later.
Whether her Master wanted to admit it or not, it was this restless longing—a prayer uttered to the Grail in the desperation and isolation of the middle of the night—that caused the Grail to answer, and bind her to Ophelia. They were both wandering souls begging destiny for love, whether they admitted it or not, and they were both audacious enough to challenge the Grail itself to answer their prayers.
The Demon King's burning gaze met Tsubaki's, and she felt rooted in place. She gasped as she suddenly saw a vision of another young woman just like her, save that she was taller with shorter hair, and a more masculine appearance. The woman was dressed like the Demon King, but also a shining, smiling white knight, complete with a large, white sword and a winged, white helmet. She was beautiful, handsome, and dangerous.
In the back of her dazed mind, Tsubaki realized she was looking at the human avatar of Caster. Rider had one too. She wasn't always a purple mermaid propelled by an eternal wave, after all, though her human self kept the purple hair. Rider's mortal guise was an ordinary girl known as Saori Hidaka. The moment Tsubaki thought of her Servant's mortal name, the other Servant's mortal name flashed in her mind too.
Aoi Miyake…! She gasped again, finally feeling some of the trance weaken, even if only for a second. What was this spell Caster had her under?
She was barely even aware of Rika's fiery taunts as their battle began, the water of Rider's wave hissing in Tsubaki's ear. Rider had just reached out to bid her Master focus when the rival Servant lunged and attacked. Blue flame burst from Caster's black body, just barely extinguished in time by Rider's wave as she again shielded her Master. It was enough to wake Tsubaki up, and for a third time she gasped. This time, though, it was like a drowning woman brought violently back to life. It was time to fight, fire and water, hurricane and inferno!
ooo
The sewers shook and the earth rumbled. Citizens in the city above felt the tremors, though they did not understand what the tremors meant. Back down below, the air was thick and heavy with tension as two, diametrically opposed powers collided. Tsubaki's song again reverberated around the cavernous halls of the sewer, breathing life and magic into all it touched, accompanied by a dark blue glow. Rider summoned a second wave so Tsubaki could travel the same way she did, and the hiss of the water was drowned out beneath Tsubaki's melodic magic.
Rika and Caster punched back just as hard. In another strange and Fateful contrast, although Rika learned about the world of mage-craft before Tsubaki, Tsubaki seemed to have a natural knack for it. Rika could cast fireballs and other powerful spells, but they were nowhere near as controlled or continuous as Tsubaki's siren song of the salty, sorrowful sea. It was up to Caster to do most of the heavy lifting, but Caster was more than happy to oblige. Black body rippling with glowing veins of blue lava, Prometheus flexed, roared, and attacked again.
"Ave Maria!" The Servant cried, appearance becoming slightly more human. He still had twisted black horns and leathery black wings, but the face that stared back at Tsubaki's was one she'd seen before, though only in a vision. Aoi Miyake!
Caster saluted the other Master with her shining, white sword, and she flashed Tsubaki a shining, white smile, her face framed by a shining, white helmet. Then dark wings flapped as a bright blade swung, blue flames hissing and curling off the side.
"All right, Caster! We'll win this battle, easy!" Rika pumped her fists. In her delusions of grandeur, blinded by the fires of glory, all the orange-haired girl could see was herself a hero, standing atop a pile of her vanquished and conquered foes, starting with the goth girl and her miserable mermaid mate! Wasn't Rika a much more palatable protagonist? And Caster, a much more magnificent Servant!
In the midst of the swirling chaos, Master and Servant were separated. Rider found herself alone against Rika. It was an easy fight for Ophelia; it was her Master she worried about… Tsubaki again hung suspended in Caster's golden gaze. Time froze and stood still as blue fire swirled all around them, intertwining with the blue light of Tsubaki's siren song. It was a blue tempest, and the young mage felt something heavy take root in the pit of her soul like an anchor. She knew the Demon King felt the same, though for him, Tsubaki was a dark spark that blazed his blue inferno.
Aoi greeted Tsubaki with a Latin phrase because Aoi could sense Tsubaki's connection to water, and not just through Rider. She was a hurricane to pray for safety from. Technically, though, Caster was Greek. But through and through—as Prometheus, Caster, or Aoi—they were a symbol of curiosity and defiance. From stealing fire for humanity, to escaping the chains and beak of a liver-eating eagle, to returning to Earth as a Heroic Spirit to continue spreading a legacy, there was a good reason the Grail paired Caster with Rika, even though she may have wanted Saber.
In fact, before Tsubaki, Caster and Rika were in combat against Lancer, who Rika initially mistook for Saber. It wasn't just Rika's usual brand of stupidity, though, rather, the childish rival Servant was just as infatuated with the mythical and legendary Saber as Rika was. Little Lancer eagerly fantasized about conquering Saber in battle and taking her coveted place the same way Rika did. Unlucky for Lancer…
Sorry kid, I'm first in line! Rika was fully prepared for Caster to deliver the death blow. The only reason the other Servant escaped was because her sneaky Master used a command seal at the very last second, spiriting them away to safety, at least for then…
Then Tsubaki strayed into Caster's orbit. That was how and why Rika found Tsubaki so fast, even in the sewers. Caster sensed her, because the Grail tied them together. Like the black, iron chains of old, Caster felt Fate itself—the Grail's dark influence—binding with him, and pulling out of him the mortal he had become this time on Earth. Aoi Miyake, those were the eyes that came forward to meet Tsubaki's, gold and silver, fire and water. Aoi could only wonder… Who was this Master, and what was she meant to mean to Aoi?
For Tsubaki, the realization was as swift as it was bewildering. In the depths of Aoi's gaze, she saw a reflection of her own longing, a yearning that stretched out across space and time. It was a sensation both foreign and exhilarating, a glimpse into a world where destiny and desire danced. Had the Grail erred in its choice of Servant for Tsubaki? She should've been disgusted by the very thought, but strangely, she found that she did not care at all while wondering about Caster… Already, Tsubaki imagined a universe where Rider had been Rika's Servant, and Aoi…
Whether they were aware of it or not, the two began to work together to keep one another alive, even as they battled. Caster and Rider never stopped trading blows, but Caster and Tsubaki both did what they could to prolong the battle. They were enemies, yes, but did they have to kill one another so soon? The battle eventually broke through to the surface world, and as the Grail would have it, a third Servant overheard them. Multiple wishes were granted that night, not just Aoi and Tsubaki's silent, shared one.
"Saber!" Rika gasped, eyes and mouth going wide as she rode on Caster's back, demonic, black wings flapping around her. Rising before them in a halo of golden light was a girl that appeared younger than all of them, though most similar to Aoi in terms of appearance. She, too, had short dark hair, though the tips were dyed yellow, golden. Likewise, by contrast, her eyes were gray-blue, and Aoi's were deep golden. Saber wore only a gi and wielded a wooden training sword, but none of her opponents was stupid enough to underestimate her.
If anything, it only spoke to her power if she considered a wooden sword a good enough weapon for her. One did not become Saber class without being one of the greatest soldiers across time and space, life and death. In fact, Saber had just finished her own engagement—a duel with Archer. Archer was powerful, fierce, and aggressive, but even her Noble Phantasm (Fiery Hailstorm of a Billion Bullets) could not stand against the lone Saber with her lone, wooden training sword. She beat the wood blade rhythmically, threateningly, against her palm, eyes closing slowly.
"Oh dear…" Rider sighed. Tsubaki understood, but secretly and guiltily, she was relieved. She cast a subtle glance at Caster as they both heard Rika gasp in excitement at the prospect of their newest challenger.
Another excuse to keep you alive just a little bit longer… And with that, fire and water rushed into battle once more, this time on the same side, but for how long? One could never be sure with the Grail's twists and turns.
AN: Listened to Träumerei and randomly thought of Fate Zero and imagined a RONDO/M4 DJ/Vocalist fire-water remix, now here we are, LOL! Tsubaki summons Rider Saori (takes her by total surprise) while Rika summons Caster Aoi (more intentionally, as Rika views herself as the Shirou Emiya of this AU. In actuality, she would be a tragic foil while Shirou-protag would've been someone else).
-Also, since all Heroic Spirits are supposed to be historical/mythological figures, my brain randomly came up with Prometheus and Ophelia from Greek myth and Shakespeare play. I know those two characters exist in Fate, but remember this is technically a D4 AU.
On that note, here are the 7 Servants as the 7 DJs:
Saber: Maho: Main protag/DJ
Lancer: Michiru: Wants to be main protag/DJ, she's a literal lancer
Archer: Shinobu: Loves shooter games
Rider: Saori: My friend who introduced me to Fate and D4's favorite Servant is Rider Iskandar, and Saori is their 2nd fav D4 girl/the one they relate to most
Caster: Aoi: That same friend's favorite D4 character is Aoi, and although they dislike Fate Zero Caster, I still made Aoi Caster as a nod to how crazy Fate Zero's Caster was
Assassin: Saki: No idea, I just know I've made her the "looks demure, snaps and becomes the craziest" in my D4-Danganronpa AU. It's not helped by her VA's wildness, or the end of All Mix Ep 6, LOL!
Berserker: Haruna: She angy
Masters can be anyone, vocalist or other, just not from the same unit as their Servant. Heroic Spirits are exclusively DJs tho, LOL!