No you're totally right, ML isn't engaged yet, the MC just twisted what he heard to suit the narrative he was expecting. I don't like that he just parroted everything the father said to the ML?
Really feels like the author didn't know how else to create conflict so they had to manhandle the characters into shallow drama.
It wasn't even selective hearing– Ichimura just straight up did NOT care about Nishino's wellbeing or feelings. He was told to his face MULTIPLE times that Nishino was unhappy with the arranged marriage and had NO plans to actually marry that girl – yet Ichimura not once takes this into consideration because he does not think Nishino's feelings matter. To Ichimura, Nishino has to bear the duty of being the business' heir by marrying whoever his father chooses. Everything Nishino is fighting against, everything Nishino does not want to let stay as-is, is essentially sensible in Ichimura's eyes. He does not understand why Nishino wants independency. Therefore, he does not understand how any of this would make him unhappy.
It's a wonder Nishino manages to like him. It's a wonder Ichimura calls this "love" when he feels it so one-sidedly.
to be fair, neither of them have much personality. but it does seem a little idiotic and maybe even OOC for MC to suggest the very thing ML said he didn’t want his father to dictate over. also, MC has some sort of selective hearing (or maybe my reading comprehension was off): the woman isn’t ML’s fiancé yet. unless he really thinks ML is a playboy and cheater… it’s kinda hard to understand how he fell in love if this is his view of his love interest. hmmm, what do y’all think?