Kyosuke never liked his step-mom and wants her out of the house after his dad died. Megumi proposes that Kyosuke can do anything he wants with her daughter, Yuna, if he allows them to stay. He allows them to stay.
Based on the ero-game by Speed, a variety of smut scenes take place as a virus spreads that turns all the infected into unstoppable, red-eyed nymphomaniacs!