Should have gone for some sort of reversal; where it turns out that the guard is a corrupt schemer who selfishly rebelled for one reason or another (like the Empress favoring other guys over him), while the "new Empress" would be good and honest.
Like this it's basically just generic isekai romance, unfortunately. Especially with the attitude of the males around the (supposedly) super-awesome Empress.
Plus ... the plot is kinda stupid. Tell the Rebell Dude that as a sign of turning over a new leaf you ordered a stay of executions. The great thing about being an absolute ruler is that (within limits) you can do whatever the heck you want, and that's certainly within those limits.
Or just friggin' abdicate if your primary concern is (not) getting murdered ...