"Kuroda Ryuuji", the main character, is a company employee.

He has feelings of hatred and jealousy toward a certain coworker at his company for having a higher position and having married Miyamai Chizuru, a woman he had his eyes on.

One day, Ryuuji finally hired a man to kidnap Chizuru's younger sister, Sonouchi Eri.

Ryuuji used this to threaten Chizuru.
The two sisters are confined.
Furthermore, in order to make them into the women he loves, their training has started.

[Translated from the official website]