Wanting to have sex, Hajime goes to his girlfriend's house for the first time, and even though they've been dating for a long time, she is still too serious and still won't let him have sex with her. He finds an unfathomable liking for her younger sister Mao, who is the complete opposite: open when it comes to sex, has a lot of weaknesses, and a bold personality... His girlfriend still won't let him have sex with her, and her younger sister is fair-skinned, big-breasted, and open when it comes to sex... And what's more, her girlfriend's sister, who is in the mood for sex, whispers dirty talk and Hajime easily falls for her, and becomes immersed in cheating sex. This is the story of a slutty guy.
