The villain is the gatekeeper, who can also change his appearance alongside his ability to overwrite a character's status and is also the king and innkeeper's husband (which I'm not a huge fan of, as his gift seems too powerful/easy to BS anything into the plot). Kenji is immune to it due to being a higher level, so the villain wants to blackmail/control Naoto to force him to get close to Kenji so he can control him that way (i e. not directly through his gift, but instead through Naoto's friendship/bond).
Depite sleeping around with nearly everyone else, the villain also kept Kazuha a virgin as some plot to make Naoto feel guilty about being forced to sleep with her (as if he had any choice in the matter, plus it's weird to me that the villain would hatch such a plan in the first place, as if he knew someone like Naoto would eventually come along and be the perfect target for this kind of thing). Then the web novel stops with the villain in the middle of raping Kazuha later on. I mean, call me weird, but I don't get how what Naoto was forced to do would make for good blackmail, much less why she needed to be a virgin for it, especially when the villain is soon raping her afterwards and making himself a prime target for Kenji's rage, anyway. It feels like majorly forced drama to me, at least, and it's wild how the web novel appears to have gone into a multi-year hiatus right in the middle of that sex scene (assuming the site I found the web novel on was complete - it ended on chapter 20 of part 3 there).