Concern

He's just been supplying her drugs and alcohol which she would take willingly.

But like is it really willingly if you are under influence

I feel like it will be brought back up in later chapters. Probably once she get everyone out the tower esp the man who will bring a lawsuit against the Duke. Everything can’t be solved at one. I think the fact he could’ve been drugging the empress the whole time could lead to death and it’s better for that knowledge to be the icing on the cake.

i think he was clearly drugging her, so the empress will follow his order
since yulia is not on her right mind she will believe everything he said
which what actually happened in the original novel

She didn't take drugs willingly Wtf

I am pretty curious how the duke was able to do so?
or yulia just let her guard down in front of the duke?
like how come he can drug her like that?
but again mentioned in one panel, he drown herself with
alcohol, man and drugs?

Well in theory in most isekai plots there is like a death scene or a transmigration scene explanation when the character wakes up in a different body for example from sickness, a bump in the head, near to death experience etc. Just a thought that the real Julia got overdose by drugs and died so thats how MC is in Julia body now ╮(￣▽￣)╭