I didn't understand what this film tries to tell, in the class, so I watched it again on YouTube. Then, I found out the message!
In my opinion, The lost thing in the film is representative of curiosity. Even though the lost thing was so big and it seems hard to ignore or not noticing, all adults act as if they are not seeing it. From this expression, I thought the lost thing is worthy for only children. At the end of the story, the main character mentions that he is becoming not noticing. I thought that means as the boy gets grown up, his curiosity became less.
