Characters
The characters in this short film are a teenage boy, a fish (mermaid), the boy's parents, and the government.
Setting
The setting of this film is a place where daydreaming is absolutely prohibited.
What the characters want
The main character, which is the boy, wants the freedom to imagine and daydream. The conflict is that people living in that distant country is completely prohibited from daydreaming.
What is real and what is fantasy in this story
In this setting, what you see is the exact reality, and imagination is the fantasy world.
What would happen after the film
At the end, the boy and the mermaid went off to the deep ocean. Therefore, to me, I think the boy decided to go to a place where daydreaming is allowed with the mermaid.
Theme/message
I think the creator wants to say that life wouldn't be that exciting and enjoyable without imagination, and that people should have the freedom to create different perspectives of looking at something.