Is it supposed to be a redemption story?
I guess, but the real meat of it must happen off screen then. Ishida learns sign language and works hard to pay back his debts before the movie begins.
He obviously regrets what he did, at least for how it hurt everyone around him.
Then what redemption is there to take place during the meat of the movie?
If the movie is about him overcoming his social isolation, then Shoko's deafness is a distraction from that story that takes up a huge chunk of screen time. That can't be it. But the ending leans that way.