Fuck his obsession with "being worthy" of Aoi. If only he knew he was already worthy the moment she chose him. If she thinks he is worthy, then he is, and no other opinions matter after that; because it's something between him and Aoi, not between him and whoever is playing opposition. If he he wasn't worthy, she wouldn't have gotten engaged with him in the first place.
And considering he was kicked out anyway, there was absolutely no reason not to keep his word on "canceling the engagement" part of the "deal". His grandpa disowned his mother, so unless he is an acknowledged heir of the Nikaido clan his grandpa's word doesn't really mean anything to Mr. Eiji Yamada.
And since he broke the engagement one-sidedly this would count as a betrayal of everyone else from the Jougasaki family who had backed him getting together with Aoi. What was the point of that manners crash course, then? Of Aoi helping him learn? This flushes the effort they already spent trying to make him "worthy" of her down the drain.
Then this opens the door to an arranged marriage problem for her... typically the final boss arc for any rich x poor romance story. Let's not even talk about the possibility of an amnesia arc which is another can of worms this chapter makes possible.
This wasn't already written well to begin with, but I can feel the writing slipping just like how his grandfather did and my rating falling like how Eiji did. We're not far from reaching
Konbini Goutou levels of hamfisted melodrama and broken neck pacing at this rate.