Karin is the shy, withdrawn adult sister he meets at his girlfriend's home, a slender recluse with no interest in sex. He sets out to immerse her in drug-fueled sex and watches her undeveloped sensuality transform into a shameless, constantly climaxing sex fiend. He deceives her about contraception before creampie sex, spikes a drink with an aphrodisiac until she begs to suck cock, chokes her through rough orgasms, and has drug-enhanced cheating sex beside her sister. By the end, she has been conditioned into an extremely submissive toy who accepts everything, cums from everything, and obeys completely.