The protagonist gets asked to work in a girls’ school which just happens to be located on an island called Lyserg which is located in the sky. The setting is a city which resembles a mid-century European town, and there, he meets many cute girlies…
(Source: VNDB)

The story follows Erina's route in the Dracu-Riot game. Erina is a foreign vampire from Russia and she is very ecchi, her conversations often involve ecchi stuff which makes Azusa really edgy and Yuuto nervous.

“Aqua Eden” – a man-made floating island where gambling, sex trade, and thievery is allowed by the government. But there is one more thing that lurks in the streets of the island–Vampires. Mutsura Yuuto is working with one of them, and together with a few other members of their group, they fight to uphold morals on the island
(Source: jCafe24)