TBH I think the best way to go about this series is to understand that their actions revolve around Madarame’s head—AKA Makio’s father—hence why Karen and Makio are trying to exhibit this happy, “functional” family whilst still having to appease him (eg: Kunimasa having to step in as the next in line, and this means he can’t choose Norio; Haruki not being able to live a normal life, because he’s always the target of the head) than it is about the romance of the main couples
(But of course this doesn’t really excuse the retcon and some redundant couples.)
TBH I think the best way to go about this series is to understand that their actions revolve around Madarame’s head—AKA Makio’s father—hence why Karen and Makio are trying to exhibit this happy, “functional” family whilst still having to appease him (eg: Kunimasa having to step in as the next in line, and this means he can’t choose Norio; Haruki not being able to live a normal life, because he’s always the target of the head) than it is about the romance of the main couples
(But of course this doesn’t really excuse the retcon and some redundant couples.)
But if anyone has questions on the plot I can answer to some capacity