Years ago, Shoya Ishida led his peers in tormenting a hearing-impaired classmate, Shoko Nishimiya. When she transfers schools, Shoya finds he has gone from bully to bullied, and is left completely alone. Now Shoya struggles to redeem himself in Shoko's eyes and to face the classmates who turned on him.

He learns sign language to apologise to Shoko for his behaviour, and so begins a relationship that will change his and Shoko's lives forever.

To make up for his past sins, Shoya has devoted himself to repaying the debt of happiness he owes. So when Shoko faces a romantic setback, Shoya assembles some familiar faces from their past for a trip to the amusement park that may just change things for Shoya, too.