Zettai Nakadashi Keihou! -Nakadashi Shinaito Jinrui Metsubou!?-

The main character is Shouichi, whose father is a scientist. One day, he visits his father's laboratory and accidentally drinks a liquid. The liquid he drinks is a newly-invented virus. It emits strong poison when touches the air. Also, you'll sexually excited once infected. To cure it, you'll need to mix it with a female's body fluid. Shouichi explains it to his father and a group of specialists is formed to deal with it... On the next day, when he goes to school, Jody, a beautiful girl, is there. Also, Maiko, a transfer student, and Hanna, Jody's younger sister, join them and they start having sex... Actually, they are secret agents. Motoka, his childhood friend, also takes part in it and an exciting battle breaks out...!