If you saw the film, you already saw the best part of it. The problem of this anime is that after the first arc (which was already covered in the film version) the story suddently stops moving forward and keeps moving in circles around the two same ideas: Amamiya (Kai's friend-rival) is frustrated about not reaching Kai's level, and the competition judges are a close-minded bunch who can't appreciate Kai's talent. Competitions become the end of the story and not just plot drives, to the point that the last 4 episodes have been a single competition. On top of that, there're no other plot lines to bring some fresh breeze into the story (as, for example, there were in Your Lie in April).
Unless you want to see some anime version of a piano competition, I can't recommend to watch it further than the childhood arc.
