Daisuke's brother, Ki, didn't have a regular job and was always bumming around, begging Daisuke for money. Ki's depraved hobby was forcibly having sex with female insurance saleswomen he invited to his home. Ki's next target was, surprisingly, Mina, Daisuke's homeroom teacher from his school days and his first love, who had switched to being a life insurance lady... Daisuke, who happened to witness Ki and Mina having sex...