In Azur Lane, the Sirens—an alien force with technology far beyond human limits—push the great naval powers into an uneasy alliance. The Eagle Union, Royal Navy, Sakura Empire, and Iron Blood initially stand together as Azur Lane, but distrust and clashing loyalties soon tear that coalition apart. As the conflict escalates, Sakura Empire and Iron Blood drift away to form the Crimson Axis, turning a desperate war against a common enemy into a struggle between rival sides.
At the center of the fighting is Enterprise, the "Grey Ghost," a seasoned combatant who carries Azur Lane's hopes for ending the war. Beneath her calm, stoic exterior, she is also a frail girl who fears the ocean, yet continues to fight because she believes it is the only purpose she has. On another front, Javelin, Laffey, and Unicorn—three ships from the Union—encounter Ayanami, a spy from the Crimson Axis, and try to build a friendship that should not exist between enemies. As battles spread across the seas, Azur Lane follows how courage, trust, and camaraderie may become the only way to reunite a fractured world.