Reiko Kobayakawa is dominated as a sex slave by Sota, her husband's stepson from his previous marriage. Every day, once her husband leaves for work, she is at the mercy of her stepson, who toys with her body freely—embedding vibrators inside her and forcing her into deep throat sessions that wrack her body with reluctant pleasure. Even as her husband sleeps beside her, she secretly receives his illicit caresses, muffling her voice while sweet moans escape her lips. But Sota's depravity knows no limits. He invites his friends over and forces her to perform sexual acts on them as well. Powerless against her stepson's intimidation, her mind wavers and her body grows increasingly sensitive, trembling uncontrollably as it succumbs to overwhelming pleasure.