Nanako started cohabiting with the precondition of marriage. Her boyfriend's younger brother, who was close to her, also lived with them. One night, she was raped by her boyfriend's brother and gave in to his body... 'Let's forget about this,' they both thought, wanting not to make him sad, trying to end their relationship, but the brother, who had genuinely fallen in love, raped her again. Knowing it was wrong, Nanako was driven to orgasm by intense sex and fell deeper. The two, knowing they shouldn't be together, repeatedly engaged in unprotected sex...
