It's not rape face; it's obsession face. It's pretty common for people who obsess over the objects of their affection to believe that "If I can't have X, no one can." The next few chapters are probably going to be some variant of Fop Sword trying to kill and/or torture Nice Dragon Lady into submission.
You can think of Fop Sword as super yandere if it helps.
@Shamz They already had a few rape/pillage scenes earlier in the series, so it's not going to be a new thing if it happens here. I agree with the "NTR keks" bit though.