The start of the game features an anthropomorphic recreation of the Battle of the Denmark Strait, where the personification of famed British battlecruiser HMS "Hood" is sunk by characters representing the German forces. The game features an eponymous military alliance, the "Azur Lane", formed by the nations of Eagle Union (United States), Royal Navy (United Kingdom), Sakura Empire (Empire of Japan) and Iron Blood (Nazi Germany). The alliance split in two because of an alien intervention, with the Iron Blood and Sakura Empire forming the opposing "Crimson Axis" faction. Using technology provided by the aliens, the Crimson Axis invades the Azur Lane's territories. The rest of the game's main plot partially follows the United States naval engagements in the Pacific War. Chapters represent several decisive battles of the war including the Battle of Midway, the Naval Battle of Guadalcanal, and the Mariana and Palau Islands campaign.