Valkyrie Drive

Valkyrie Drive (ヴァルキリードライヴ, Varukirī Doraivu) is a Japanese media franchise created by Marvelous. The franchise consists of three projects; 'Mermaid (マーメイド, Māmeido), an anime television series produced by Arms Corporation, which aired in Japan between October and December 2015; Bhikkhuni (ビクニ, Bikuni), a PlayStation Vita game released on December 10, 2015 in Japan with a Western release in 2016 and a Microsoft Windows version in 2017; and Siren (セイレーン, Seirēn), a social game for iOS and Android devices released in December 2015.

Plot
Suddenly, girls all over the worldhave been infected with a mysterious virus known as the A Virus (Armed Virus). These girls are divided into two classes; Extars, who can transform into weapons when sexually aroused, and Liberators', who have the power to wield an Extar's weapon form, known as Liberator Arms, through a process known as Drive. These girls are brought to separate islands to spend their days completely isolated from the rest of the world until the islands' Observers, authorized by the government Organisation AAA, ostensibly deem them ready to rejoin society again.