Koe no Katachiis a good, but very uneven manga. The story is really about Shouya and him dealing with a wide range of issues that include low self esteem, depression and social anxiety and to that end the cast mostly serve as props as he deals with all of these issues.

In many ways, the story is quite idealized as Shouya never does anything reasonable about his situation, nor do any of the adults do anything reasonable like suggest he seek professional help. This is particularly jarring after his mother discovers he had intended to kill himself! On one hand you have to be forgiving about this because it's just light entertainment, but on the other hand it sends a strange message to young readers about how to deal with mental illness and depression.

All of that aside, the good parts of this manga is the awkward relationship between Shouya and Shouko, but the bad parts of it involve common manga tropes around people being oblivious to feelings and unable to communicate their intentions clearly. In that way, it's quite stereotypical, which for such an unusual set-up is a bit disappointing.

Koe No Katachi, despite it's unusual premise, isn't a very unusual story. It puts perhaps too much focus on the idea that "getting a long with people" and "being a good part of society" is the way for people to feel good about themselves, and is less introspective on the feelings that motivate people to engage in anti-social behavior. There is one shining example of a character acting like a normal human being and that's when a side character, Mashiba, stands up to an adult that is clearly in the wrong. Sadly Shouya doesn't really follow his lead, nor seem to really grow from the experience.

If you can look past the faults of this manga, there is an enjoyable and sweet story here that's well worth reading, but there isn't any real wisdom or messages that I think people should internalize. The good parts are really good, but ultimately Koe no Katachi suffers from some uneven pacing and simplistic moralizing.