Narrator POV

Akagi used Siren tech to transport Azur Lane into another dimension where they were surrounded by Sirens and everyone started fighting each other. 

The vast expanse of the ocean turned into a battlefield. Columns of smoke from Siren wreckage spiraled into the sky as the Sakura Empire and Iron Blood fleets clashed against the combined forces of the Eagle Union and Royal Navy. Despite their damaged condition, mass-produced Siren ships pressed forward, launching devastating barrages that lit up the horizon in bursts of fire and chaos.

Leading the charge for the Sakura Empire, Akagi, Kaga and other Carrier girls directed their planes with precise commands, their riggings brimming with energy. At the forefront of the Iron Blood fleet, Prinz Eugen cut through the waters with her trademark smirk, her guns blazing with calculated ferocity. Beside her, Z23 coordinated with the Sakura destroyers, their movements sharp and deadly as they disrupted the Azur Lane lines with relentless torpedo salvos.

From the opposing side, Enterprise stood tall, her aura commanding as she launched another wave of aircraft. Cleveland and her sisters battled Siren cruisers with grit and determination, their teamwork a sight to behold. Hood's elegant presence belied the devastating power of her broadsides, while Queen Elizabeth, from her central position, orchestrated the Royal Navy with regal authority. Belfast, leading the maid corps, dashed to the battlefield to escort high-ranking members of the Round Table.

Amidst this chaos, the ocean itself seemed alive, carrying the cries of battle as if feeding on the discord.

Meanwhile

Far from the main battle,the flaming object cut through the storm like a comet. Rain lashed against its fiery surface, but the flames refused to waver. The storm, almost sentient, seemed to part in its presence.

Suddenly, the owl beeped in alarm. Red lightning illuminated the sky, and he quickly evade all. The bright red flashed too strong that he covered his eyes not to blind. He felt something wrong. When he opened his eyes again, the sea somehow calmed surrounded by many black structures with red highlight. From the portals emerged a swarm of Siren vessels, their sleek forms bristling with weapons. They moved with unnerving precision, pointed their cannons at Y/n.

Y/n:"What a warm welcome from Siren!"

The Sirens opened fire, their weapons unleashing a storm of purple energy beams. He dodged, weaving through the barrage with the agility of his Pretanodon form. A quick twist and dive brought he into the heart of their fleet to create a huge explosion combined fire, thunder and wind. The blast rippled outward, vaporizing the closest ships and sending shockwaves that capsized and burned software of others. The energy cleared a path through the swarm. When he slowly stood up, all left were wreckages.

???:"What a performance you have, Y/n?"

Another portal tore through the fabric of this warped dimension, and a figure slowly appeared with manta rigging on her back while her arms attached on it. Her rigging shimmered with pulsating yellow energy. Her sharp, predatory eyes locked onto Y/n, and a sinister smile curled her lips.

Y/n:"I assume you have some relationship with Omitter, right? I wonder what purpose you drag me into this place. What're your name, beauty?"

???:"My, why thank you for compliment. My name is Tester, and about Omitter. Well, you can say that we are like... What is the word that human use to call someone closing with you? Acquaintance? No. Comrade? Not that."

Y/n:"Friend?"

Tester:"Yes, that's right. Thank you again."

Tester: "But enough small talk, Y/n. You're a fascinating anomaly. A being so different, so... unpredictable. I'm here to stop you interfering our plan. So, can you die here?"

Countless Siren ships emerged from portals, drones buzzing ominously, their weapons primed.

Y/n: "Oh? Is that all you got?''

Tester:''Because of your appearance, my friend has prepared these riders, or whatever they called, for you only. Enjoy!''

She dispeared in her own portal, and two portals opened. As the portal shimmered and faded, Y/n found himself staring at two ominous figures. 

(Kamen rider AnotherPara-DX, just colorless version of Para-DX. Also he armed with Gashacon Parabragun)

(Kamen rider Ryuga, coldblood dragonic rider. One of my favourite dark, anti rider)

Y/n( quickly put Juuga driver on his waist):''Not only ZAIA, but also Ryuga and Another Para-DX! The Sirens can make copy of riders. How interesting! HENSHIN!''

Another Para-DX used Gashacon Parabragun in Gun Mode to fire a volley of black energy blasts, and Ryuga surged forward, his Dragsaber gleaming in the dim light as it crackled with dark flame.

Ten colored animal constructs (including a violet Tyrannosaurus Rex, magenta Megalodon, green Eagle, red Mammoth, tangerine Pteranodon, gold Lion, yellow Jackal, orange Gorilla, blue Mantis, and pink Brachiosaurus) surrounded to shield him, deflecting the incoming attacks. Jackal and Mantis engaged Ryuga, while Eagle and Pteranodon assaulted Another Para-DX. When the attack had been cancelled, all constructs emerged with Y/n as colored lights to form Juuga armor. 

Those two continued to attack. Y/n summoned Attache Rifle in left hand to fire back Another Para-DX and Thousand Jacket in right to stop a slash from Ryuga. Sparks erupted on impact, lighting up the swirling storm around them. The clash between Y/n and the two dark Riders sent shockwaves rippling through the distorted battlefield.

"Advent! Strike vent!" Dragblacker  come out from nowhere, and Ryuga has armed with Dragclaw. 

"Dual Gashatto! Kimewaza! Clone! Steel up! Muscle up! Perfect Critical Finish!" Another Para-DX collected Energy Item to create clones of himself, while Gashacon Parabragun covered in red energy, pointed at Y/n.

Seeing this, he smirked behind his visor while holding Jackal Vistamp on his hand. He quickly scanned it on Rider Absorber of his driver and pulled Juuga Vistamp to the side. "Absorb! Ex-aid! Jackal Critical Attack!"

Ryuga with Dragblacker launched black fireballs while Another Para-DX and his clones performed several powerful consecutive blasts, which enhanced Iron-Body, causing a explosion. As the explosion rocked the battlefield, smoke and debris obscured everything, leaving only the sound of crackling flames and the low hum of Siren energy signatures.

From the smoke, many yellow energy blasts were fired from Attache Rifle, targeting Another Para-DX's clones. Those clones has been destroyed instantly, and Another Para-DX had to switch Gun Mode to Ax Mode. Another Para-DX had to take golden blast, and he could not deflected it because of its power. Eventually, an explosion erupted, and the word "PERFECT" flashed as Another Para-DX was defeated. The only thing left is his broken Gashat.

A gust of wind scattered the debris, revealing Y/n, unscathed, his armor glimmering with absorbed power from the Jackal Vistamp. Holding Attache Rifle, he gave a hand signal that Ryuga should continued.

"Final vent!" He jumped into the air with Dragblacker flying behind him. Y/n still smirked, then he summoned Thousand Jacket again while took Attache Rifle back to his Dimension Pocket. He scanned Komodo Dragon Vistamp, and pull Juuga's to the side again. "Absorb! Ryuki! Komodo Dragon Final Attack!"

Dragblacker then breathes dark blue fire at Ryuga, propelling him into a flying kick that strikes Y/n. Y/n charge the red energy from Vistamp into Thousand Jacket, creating a flamming slash. Their clash sent shockwaves across the dimension. Ryuga's dark kick met Y/n's blazing slash in an explosion of red and black. When the dust settled, Y/n stood triumphant with the broken Ryuga's deck floating near his leg.  

Tester:"Now you're becoming so annoying. I guess i have to use this way to eliminate you."

Her voice echoed in the space while the Siren structures and ships tried to self-destruct. The Siren structures began to self-destruct, creating a chain reaction of explosions. Y/n braced himself, his eyes scanning the battlefield for a way to escape as the chaos unfolded. The dimension started to crack. Seeing this scene, she assumed he was death, even if he could survive the explosion, he could not escape from this space. She left this Mirror Sea.

Location: Mirror Sea (Main battle)

Enterprise was reawakened with sinister glowing eyes and even the Observer commented that Enterprise is the "Key" no matter in which time era. Enterprise then fired a shot at Kaga which she fell into the ocean. Enterprise's body suddenly releases a large amount of energy that covered everyone in the ocean.

 To be continued