夫の背負った借金2000万円の身代わりとして、高利貸し・佐川の家政婦となった人妻・あき。借金免除を条件に、執拗な乳首開発と中出しによる返済交渉がはじまる…。恥じらいながらも全裸となり、綿棒や筆による愛撫で乳首を徹底的に開発。ロータースティックや吸引おもちゃを用いたチクハラ攻めにより、乳首のみでの潮吹き絶頂を経験。日を追うごとに抵抗感は薄れ、「もっと乳首いじってください」と自ら開発を懇願する肉体へと変貌していき、ついには夫の目の前でエロ衣装に身を包んだあきが自ら敏感になった乳首をこねくり回しながら浮気生ハメを要求してしまう…。

Aki, a married woman, becomes a housekeeper for loan shark Sagawa as a substitute for her husband's 20 million yen debt. In exchange for debt forgiveness, negotiations begin involving relentless nipple stimulation and unprotected sex as repayment… Though embarrassed, she strips naked and her nipples are thoroughly stimulated with cotton swabs and brushes. Through nipple ******* using vibrator sticks and suction toys, she experiences orgasms and squirting just from nipple stimulation. As the days go by, her resistance fades, and she transforms into a body that begs for more nipple stimulation, and finally, in front of her husband, Aki, dressed in erotic clothing, kneads her now sensitive nipples and demands unprotected sex with him…