 If you liked
Koe no Katachi
|
 ...then you might like
Hitori to Hitori no 3650-nichi
|
Despite coming from two entirely different genres, I cannot help but recommend this manga. Both stories feature a bully who regrets his actions so much that he ends up becoming someone with crippling anxiety and a lot of self loathing, someone who's completely given up on life. However, ultimately, it's his childhood victim who becomes his savior and helps him see the beauty in life again.