The ML swapped the MC's medication with calcium pills and another similar type of pill I think? It was done with good intentions because the ML believes the medicine the MC currently takes for his social anxiety can be harmful to the body (though I wonder if he found that out through Google/Baidu or something). However as someone who isn't knowledgeable about that area of study, he shouldn't have done that, especially without the knowledge of the patient (or even trying to discuss it with him to get it done through the appropriate channels). It's just wrong and (potentially) dangeous on so many levels. (Has he ever heard of withdrawal symptons? Does he understand how frightening it would be to experience that and have no idea why? His doctors would also be under the misconception that he's been on that medication ans plan accordingly. And that's only a small part of it.) If I read further, maybe I'll find out something that would soften the blow. But as of now this is how I see it.
he threw her out of the carriage when she's was chattering too much while he's trying to rest. Or maybe he was just annoyed about her insulting his favorite carriage. (You can judge their actions once you get to that part.)
They've got the "I think this guy is such a bastard but I feel weirdly attracted to him, " "he also has a beautiful ex-girlfriend who still has feelings for him and I feel inferior and hi now she's coming over to sneer at my unsuitability to be his partner, " and a "no one believes me when I say I can see dead people but this guy says he does because it's me saying it even though we haven't even known each other at all outside of this fake fiancé arrangement besides (oh I just remembered!) that one encounter when we were kids and you gave me ice cream. Of course you remember it like it was yesterday."
handing over his entire company to a lover who has shown no capability in managing one (has he even graduated?), has a known and established tendency to act foolishly and thoughtlessly (an "endearing point"), is someone he has only known the existence of for less than a year, and has only been in a relationship with for a couple of months. Look, dude, no matter how much you love him and no matter how much you want to show that, you don't make someone like that the boss of the company you made.