Kan`in no Gakuen - Season 1

Kadomori Shizuku leaves a mysterious message for her classmate Hosokawa Seiji, with whom she has just shared an intimate encounter, asking what one would do with power enough to shape the world. She then vanishes. Her twin sister Kasumi senses something is amiss and witnesses Shizuku invoking the unnatural power of the Kadomori family to open a forbidden gate, an entrance her lineage has been tasked with guarding for generations. Declaring her need for power, Shizuku disappears through it. To pursue her, six girls destined to guard the portal gather around Kasumi and together open the gate to an unknown world. There, a mysterious girl named Sora appears before them, as they confront inescapable destinies.