I've seen high profile short drama manga with worse development before, especially the character building, title is "Dear Sa-chan".
This manga is good and actually have movie format, every characters are clearly written what is their true nature
I'm glad this is not milked too much like Koe no Katachi / A Silent Voice which add a long unnecessary filler chapter which is scrapped during making the movie or Seo Kouji's work which the story flow goes nowhere just to prolong the serialization. Even if this is axed, it is satisfying.
Too bad the manga sales is low because young people don't like soap drama story