3 ideas
A small black fish living with its mother in a mountain stream asks where the stream ends, and the neighbors, who insist the world is only their pond, call it a troublemaker and want it punished. It leaves anyway.
The fish states the book's ethic directly. It will not seek out death while it can still live, but when death is forced on it, what matters is the influence its life or death has on others. Survival is not the goal, and neither is martyrdom for its own sake. The unit of value is the consequence of a life for other lives.
The tale is framed as a bedtime story that an old grandmother fish tells to twelve thousand children. When it ends, eleven thousand nine hundred ninety-nine go to sleep. One little red fish lies awake thinking about the sea. Read this way, a subversive story does not need to persuade everyone; it succeeds if it keeps a single listener restless, which is why a children's fable could be treated as dangerous enough to ban.