Toshishita Koakuma no SM Kanrijutsu

At the young age of 29, Minato Kashiwagi is already the chief director of her department due to her hard work. However, she has a dirty little secret-she enjoys disciplining all the docile men at work! She burns off stress punishing these men until one day a young man, Towa, starts to work at the company part-time. The moment Minato saw Towa's cute, meek face, she knew he'd be obedient! So, on the night of Towa's welcome party, she sneaks out with him in an attempt to rule over him in bed. But…
(Source: Renta!)
Note: Includes an extra chapter.