He actually does.
The whole movie is about him being shunned/bullied by his friends (who also bullied her) and everyone else.
He grows up, develops social anxiety and wants to kill himself because he hates himself that much for the way he treated her. Only not going through with it because he wants to make it up to her, even though they were actual middle schoolers when this occurred.
He learns sign language, helps her sister and practically dedicates himself to her, and the entire message is a beautiful one. That you can always atone for what you've done and anyone is capable of change and becoming a better person.
How ironic that message is lost on Twitter users.
Been a minute since I talked about ships related to #Sinkids, so im gonna make a poll on Lemy ships I like in particular which one of them you guys like the most.