Haraguro Onzoushi ga Ijiwaru Desu

Office worker Shiho, age 28, plays the go-getter career woman so well that everyone at work calls her the "Iron Lady." Feeling uneasy about her relationship with her boyfriend Ken, Shiho takes the leap and invites him to a company party, but as the party begins he's still not there... In that moment, her handsome coworker, and heir to the company, Miyagi strikes up a conversation with her. Miyagi is a big hit among the female employees, but Shiho has always treated him casually, never taking much interest in his charms. However, when she runs into him again on the way to the bathroom, the usual sweet and chipper Miyagi is nowhere to be found! His speech is rougher, and he's dropped the workplace niceties, and on top of that he backs her up against the wall, blocking her retreat with his body...?! An office romance with a high-class bachelor, at once wicked and earnest, who just might be her Mr. Right! (Source: MangaPlaza)