Setting: A boy that likes fantasy lives in a country that fantasy is banned. Any time.
Conflict: Though the boy likes fantasy and he believe he saw mermaid, fantasy is banned in the country so the government try to stop him having fantasy.
Symbol: If he can find the mermaid, he can prove his innocence. So I think the mermaid symbolize the freedom of thoughts.
Irony: He can't see the mermaid he caught after he come back home. But finally he could find a mermaid in sea and he followed the mermaid.
Climax: He escaped from government and came back home to find out the mermaid. Thought he could see the mermaid then, he went to the sea and his innocence was proved.
Theme: No one can control people's thought and rob their freedom of thoughts.