The so-called blue bird is the bird that brings happiness
When time wears away the beauty of all things in the world, the "happiness" between us will become more and more beautiful in the torrent of time.
Helsin has had a dream since he was a child, that is, when he grows up to be a wrinkled old grandma, there will be someone who has also become a wrinkled old grandpa to stand beside him, smile and call his name, and then die together.
That was happiness, the humble happiness of the two of them.