Azur Lane, a combination of all the different Camps in the world, was once successful in repelling the underwater menace, the Siren. Now splintered, they must face a new threat in Red Axis, former allies who crave to wield this otherworldly Siren technology for their own nefarious desires! Who will be victorious in the never-ending war between these battleship girls!?
Upon learning that former Azur Lane alliance members Sakura Empire and Iron Blood are ready to go to war, forces from the current Azur Lane, Eagle Union and Royal Navy, assemble at a forward base.
The Azur Lane base was hit hard when the Sakura Empire suddenly struck. As the Royal Navy and Eagle Union forces scramble to finish repairs, the Red Axis prepare another strike, this time against forces in the open seas.
The Royal Navy battle-maid Belfast arrives, forcing the Red Axis to retreat. There is no longer any doubt that Enterprise is key to the success of the Azur Lane alliance, but it is also evident that her problems are more serious than simple hull damage.
After their successful strike against Azur Lane forces, the Red Axis fleet returns to Sakura Empire. Akagi checks in on the progress of her grand plans, and Ayanami regroups with her peers and reflects on the battles she just fought.
Sheffield and Edinburgh take shelter on a small island to evade the Red Axis fleet pursuing them while awaiting reinforcements. A major confrontation seems inevitable, but members of both sides of the fight have doubts and concerns.
The rescue mission is a success, allowing Azur Lane to learn about Akagi's Black Cube. Both alliances regroup at their respective bases to plan their next moves, while getting some much deserved rest.
Azur Lane forces advance into the open seas to take on the Red Axis. Under Akagi's command, the full Sakura Empire navy assembles to meet them. As Observer watches from outside the battle, the two forces collide head-on.
With Kaga and Akagi defeated, Sakura Empire forces are sent into disarray. Enterprise, after activating a mysterious and overwhelming power, also goes missing. Both forces scramble to regroup, to put an end to this battle.
Ayanami saves Zuikaku and Shoukaku from Enterprise's relentless attack, but is injured. She regains consciousness in the Azur Lane base as a prisoner of war.
Enterprise is haunted by recurring nightmarish vision and unable to fight. Akagi is missing, presumed dead. Without their flagships, neither Azur Lane nor Red Axis are able to make a move. The Sirens are determined to change that.
Kaga launches an attack against her own camp to reveal the Orochi and joins forces with the Sirens. They launch a weapon of mass destruction, forcing the Azur Lane to react. The Red Axis fleet regroups to pursue the Orochi.
The Orochi proves to be much more powerful than the most advanced technologies humanity has to offer, and Enterprise is knocked out by a huge explosion. The battle is at its final phase as each combatant faces the truths they seek through battle.
