His father remarried and his new mother was only four years older than Hajime. Hajime's new life with his young stepmother Saki always made him lust after her beautiful, busty, and youthful body. Hajime, who is studying at the pharmacy department of a university, secretly gives Saki an aphrodisiac by compounding some substances he has obtained. After a few days, changes begin to appear in Saki's body... He can't help but crave his young stepmother's body... Saki has become a slutty woman who is high on the aphrodisiac, and he devours her every day.