The client, whose boyfriend was stolen by her best friend, called and said, "I don't care what happens anymore," adding, "Send me hidden camera equipment immediately for revenge." We promptly delivered the surveillance devices and began covert recording. It was confirmed that her trusted boyfriend was having an affair with her best friend. With our support, the act of cheating sex was fully recorded. Based on information that the boyfriend and the best friend frequently visited each other's homes, camera installation proceeded smoothly. As a result, two schoolgirls, betrayed and sold out by their best friend, were involved.