I mean, neither of them have to divulge anything about their engagement, I don't understand how this is a major event. "Oh yeah we were switched at birth so here we are"
There was so much potential for this to be an awesome tragedy: the mc falls in love with the aki but aki feels betrayed and hates him, yushino is in love with the mc but the mc hates her, and fujinomiya gets a real backstory that isn't "I saw him that one time"