Riko is a plain office lady with glasses and untrimmed bangs. One day, while working overtime, she has a physical relationship with a playboy colleague she had a crush on. Riko, who is extremely shy even about showing her naked body, transforms after one fuck! She overwhelms her colleague with the techniques she learned from the erotic manga she had been reading every day, leaving him limp. The offensive and defensive relationship between the two is repeated in the office.