Following a catastrophic earthquake twenty years prior, Tokyo, along with most of the world, has sunk into the ocean during a large-scale land subsidence. Aika Sumeragi is a salvage agent, a person who digs up submerged artifacts from the cities below. She works for a small company run by Gozo Aida, and takes on fairly dangerous jobs. In the first story, she and Gozo’s daughter Rion, search for material called the Lagu. However they are captured by Rudolf Hagen, an effeminate but over-sexed man who wants to use the Lagu to transform the world, destroying its inhabitants, and replacing them with an army of young women called the Delmo Corporation who will carry his progeny. Alongside Hagen is his obsessive sister Neena, who is jealous of Aika when Rudolf desires to have Aika for himself. Aika has a special bustier that, when activated, transforms into a battle bikini that gives her extraordinary fighting powers. Following the defeat of the Hagens, the Delmo Corporation girls seek other methods to foil Aika in episodic stories.