Yu Yu has had a poor memory since she was a child and always forgets things. So everyone gave her a nickname:
"Fish" because fish only have seven seconds of memory.
But she will always have someone to help her clean up the mess, and she doesn't seem to need to be a sensible child.
Later, Chen Yi lied to her because he clearly said that he didn't need her to grow up.
"Chen Yi, are you serious?"
"If you had, how could you be willing to leave me for so long?"
Purpose: Childhood sweethearts