Koe no Katachi follows Shouya Ishida, an elementary school boy who tries to crush boredom in cruel ways, and the deaf transfer student Shouko Nishimiya, whose arrival in his class turns petty mischief into open cruelty. Shouya and the rest of the students bully Shouko for fun, but after Shouko's mother notifies the school, Shouya is singled out and blamed for everything done to her. When Shouko transfers out, he is left to face the consequences of his own actions, and he spends the rest of elementary school and middle school being ostracized while the teachers turn a blind eye.
By his third year of high school, Shouya is still haunted by what he did as a child. Consumed by regret, he sets out to seek Shouko once more and try to make amends, even though he cannot know whether she will accept him. Koe no Katachi traces that reunion and the difficult path toward redemption, following Shouya's honest attempt to atone while the shadows of his past continue to follow him. In the process, the story becomes a quiet drama about guilt, forgiveness, and the possibility of starting over.