An elementary school student, Shōya Ishida, along with his friends, cruelly bullies Shōko Nishimiya, a new classmate who is deaf. As the bullying escalates, the principal learns of the situation, but in a twist of fate, Shōya's friends turn on him, framing him as the primary instigator. This leads to a confrontation between the two, ultimately causing Shōko to transfer to another school, while Shōya keeps her notebook as a memento.
Transitioning into middle school, the stigma of being labeled a bully haunts Shōya, causing him to retreat into a shell of loneliness and depression. He contemplates suicide but resolves to seek redemption by mending relationships and apologizing to those he's harmed before taking that drastic step. This journey of atonement brings him full circle to Shōko, where he returns her notebook at the sign language center she attends, only to discover that she is still deeply lonely and reserved.
In this new chapter, Shōya forms a friendship with Tomohiro Nagatsuka, a fellow outcast who feels a sense of gratitude towards him for standing up against bullying. Attempts to help Shōko find joy in the little things lead to friction with her younger sister, Yuzuru. A series of misunderstandings escalates when Shōya jumps into the river to retrieve Shōko's notebook, only for Yuzuru to take a photo of the moment and use it against him, resulting in his suspension.
As the story unfolds, Shōya strives to reconnect Shōko with former friends, including Miyoko Sahara, a compassionate peer, and Naoka Ueno, who has a dubious history of bullying. Relationships entangle further when Miki Kawai enters the scene, rekindling connections while also revealing secrets that cast shadows on their friendships.
After navigating the complexities of emotion and misunderstanding, Shōya invites Shōko on a group outing to an amusement park, where tensions flare and emotions boil over, causing a fallout among friends. As the weight of their shared past presses down on him, Shōya turns inward, finding solace only in his bond with the Nishimiya sisters.
During a poignant fireworks festival, a moment of despair drives Shōko to the brink. Shōya races to stop her from jumping and, in the process, ends up injured and comatose. In a dreamlike encounter, Shōko is visited by Shōya, where he finally voices his regrets, urging her not to carry the burden of guilt for his struggles.
When Shōya awakens, he must confront both his past actions and his future. His journey leads him back to the bridge where he finds Shōko grieving. In a heartfelt exchange, he offers apologies and reconciliation, vowing to embrace life with her support.
Returning to school, Shōya experiences overwhelming joy as he reunites with his friends, realizing that their care for him remains strong. As they head to the school festival together, tears of gratitude and relief flow as Shōya understands that he has begun to find redemption and healing in the connections he's sought to rebuild.
