Equation of immorality / Immorality

The main heroine of the hentai, Sayako, is a special agent of a secret military organization. She is assigned a new task - to search for sources of drug supply to the country. She transfers to Mikami Institute where she takes a position as a teacher. Soon she becomes the object of desire of one of the students - Yuniichi Yano because of her resemblance to his deceased mother. He likes to film everything and Sayako will not just conduct an investigation while he constantly follows her around...