Mamori Tokonome, a girl who was diagnosed with an irregularity in her body, is captured by agents and taken to a remote island known as Mermaid. There, she is attacked by two girls named Miyasato and Kouzuki.

While Mirei is locked away in a disciplinary room, Mamori wakes up in the care of Kasumi Shigure, commander of the Welter, who explains that all the girls on the island are carriers of something called the Armed Virus.

Mamori and Mirei are picked up by Meifon, who takes them to a small town run by Torino Kazumi. Charlotte learns about Meifon repeatedly stealing supplies from Welter.

Surrounded by Welter soldiers, Rain kisses Mirei to transform into the Disarmment Buster Arm. Lady J uses her skills as a motorcycle to fight.

Mirei, Mamori, and Kasumi come across a girl named Nimi Minimi after running away from the castle.

Meifon works with Hyouko Yundou and Futaba Kirii, to steal more goods from Veste while also making money from gambling. Meifon arranges for Mirei to enter a beauty pageant being held at the Mermaid Festival.