Still don't like the ex btw, though he's pretty decent for trying to be a man and ask her if the children were his (and possibly try take responsibility)
I suspect virginity isn't the issue here. This guy works for the company and is trying to rekindle an attachment with her. It's likely because of her perceived relationship to the CEO. That could bring a lot of problems of trust. Soohyuk is already paranoid to the point of OCD because of his family. He surveils her more than is healthy because that's "normal" due to the power struggles inside the company. If he finds out that she's hiding any part of this relation from him that may trigger his defenses. If he mispeaks in anger about this later and calls her "dirty" in any way like an OCD sufferer could that can very easily be misunderstood. Soohyuk's got some major issues that are being glossed over right now. That's one of the reasons his secretary is being vigilant about his relationship with Taehee.