An incest story between the devilish little sister "Iroha" and her quiet brother. The more the little sister thinks that there is a line that must never be crossed, the more excited and passionate she becomes. She seduces and seduces her serious brother with her insane and lewd provocations! Gradually, the brother's reason crumbles, and in the end, he gets what the "devilish little sister" wants...!?