In the Millennium Tree Forest, a girl speculates that once a sapling has taken root, she’ll have become an adult; she also wonders if she’ll be alive by the time it becomes taller. She continues to imagine that, once the sapling has grown many leaves, the world will have changed even more than it already has, wondering if her sins will have been forgiven once the sapling becomes a tree. The girl notes how, to a tree, a millennium would be the blink of an eye and she prays to the tree for an eternity of peace.
The song's title refers to Rin's reflection on how a thousand years would be like a blink of the eye for the tree sapling.
According to mothy, the song was given a shorter title compared to many of his other songs because he felt it didn't need to be overly long or complicated; he clarified that the song itself still packed a lot of emotion.