Odc. 1: Mamori Tokonome i Mirei Shikishima walczą z Liberators na Wyspie Syren

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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, the former being a Liberator who arouses the latter, an Extar, to transform her into a gun known as a Liberator Arm. Just then, another girl by the name of Mirei Shikishima arrives on the island, protecting Mamori by transforming her into a sword, allowing her to defeat Miyasato and Kouzuki and escape to the jungle. Arriving at a white castle, Mamori and Mirei are trapped in a colloseum, they are confronted by another Liberator, Saejima, who uses one of her masochistist slave girls to bring out a ball-and-chain Liberator Arm. Just as the two are cornered, Mirei once again uses arousal to transform Mamori into the sword Liberator Arm, allowing her to defeat Saejima in an instant. (Source: Valkyrie Drive Wiki)