Asside from knowing his childish and irrational personality, he's also shown to not complete any of the paperwork like his asistant is constantly yelling at him for that. His incompetency also shows when he's unable to find a load of assassins that are literally in his own palace like what? At first he even pushes aside the search for the assassins who have made around 3 attempts to kill her already, just because he doesn't like her or smthn idk other than her loving him I don't think it ever mentions any solid reasons as to why he hates her- it's just, "I love my concubine so I can't love you, so fuck you stop coming to see me even though I'm married to you, by simply existing you have hurt my concubine even though she's said to me that you're chill with her". Oh, also the Empress comes from an influential family so I suspect if she was killed because the Emperor couldn't protect her then there'd be some sorta conflict. Unless I'm uh reading too far into it, since this is a fairly light hearted manwha(that's not a bad thing though, it's very cute). But even if I were to ignore those things he's still a shit character and how dare he fall in "love" with our strong Empress.