When the "Sirens," an alien force with an arsenal far surpassing the limits of current technology, suddenly appeared, a divided humanity stood in complete solidarity for the first time. Four countries—Eagle Union, Royal Navy, Sakura Empire, and Iron Blood—formed Azur Lane, paving the way for the improvement of modern warfare, which led to an initial victory against the common threat. However, this tenuous union was threatened by opposing ideals, dividing the alliance into two. Sakura Empire and Iron Blood broke away and formed the Red Axis, and humanity became fragmented once again. As a seasoned and experienced fighter, the "Grey Ghost" Enterprise shoulders Azur Lane's hope for ending the war. But behind her stoic persona hides a frail girl, afraid of the ocean. Even so, she continues to fight as she believes that it's the only purpose for her existence. Meanwhile, Javelin, Laffey, and Unicorn—three ships from the union—stumble upon Ayanami, a spy from the Red Axis. Strange as it may seem, they try to befriend her, but as enemies, their efforts are for naught. Still, they persevere in hopes of succeeding one day. Amidst the neverending conflict within humankind, the keys that could unite a fragmented race might exist: a soldier coming to terms with her mysterious personality and camaraderie between those with different ideals.

In a seemingly peaceful time without looming threats of Sirens or war, shipgirls from different nations live together in harmony. Some girls, such as the destroyers Ayanami, Javelin, Laffey, and Z23, attend school. Others immerse themselves into various other activities, including sports, foraging, training, going to formal parties, or even vying for the commander's attention! But one thing is for certain: the girls will continue to deepen their friendship in the pleasant port of Azur Lane!

The beginning of the Taishou era spelled the end of the tanuki's tricks. These raccoon dogs, who are able to transform into human beings, used to love fooling humans until advanced technology rendered their endeavors futile. However, Mameda, a young tanuki girl, has not given up on this tradition, and—resolved to follow in her father's footsteps—travels to Osaka in hopes of duping people. As others in her village predicted, Mameda fails to deceive a single person, and she is even hunted down by an angry crowd. After finding refuge in a theater, she stumbles upon a rakugo performance given by a master of the art, Bunko Daikokutei. Fascinated by the vivid images created by the rakugoka's acting, Mameda becomes enamored with this style of storytelling and decides to become Bunko's apprentice! Despite her initial reluctance to take a disciple, Bunko begins to teach Mameda rakugo after witnessing the young tanuki's perseverance. Between undertaking a taiko apprenticeship, handling her work at the theater, and memorizing plays, Mameda needs to give her all if she ever plans to master the only art that still has a chance to fool people.