Shachou! Watashi wa Anata no (Dansou) Hisho desu.

Rei Usui was looking for a high-paying job to help pay off her father's debts when a mysterious man makes an offer with a salary that's too good to be true. He wants Rei to dress up as a man and become the private secretary for his son, Minato, in order to help Minato overcome his fear of women. However, Minato turns out to be rather arrogant and unpleasant. Will Rei be able to complete her cross-dressing secretarial duties without Minato finding out?

(Source: Hakusensha, translated)