Valkyrie Drive: Siren - Breakout

Tokonome Mamori is transferred to "Mermaid"—an artificial quarantine island for people with superpowers. When Mamori is attacked, a newly transferred girl named Mirei saves her. The enemy doesn't stop, however, and the two are soon cornered. Just when they think all hope is lost, Mirei kisses Mamori, and Mamori turns into a sword. Mirei then wields the sword and launches a counterattack against their enemies. (Source: Anime News Network)

This spin-off tells the story of the girls who have the VR-Virus and live on the island of Bhikkhuni.