@megagen
That's what bothered me the entire time while reading this. If he was known to even kill a child of an enemy, who wouldn't think he finally went full on insane for barking at an innocent man for "stepping on his wife's shadow"? A shadow, my dude. He also mentioned if the emperor ever found out the truth of him being influenced by magic, his reputation wouldn't do so well. Let's not get started by the fact that we the readers don't even know the clear rules as to the duke switching from normal to Lex.
(Oh, but if you look at it this way, the MC was extremely malnourished from love ever since the death of her mother. Perhaps she has some form of 'illness' in her head that makes her draw the childishness out of her and behave like this for an an adult.)
At best, this story can be fun to read at times. At worst, it's just a mess of a storywriting. Imo not exactly uncommon in a lot of the popular romance manhwa. Poor ML though, here the author is trying so hard to portray MC as the victim (she is and she isn't at the same time), but ML is the one having no control of his body whatsoever, banged someone he didn't even know.